Never.

Ok almost never. By staying on the older plan I get a lower rate. I think I changed four years ago because the cost was basically the same but got more data. Before that... It was a long time ago

Never. $25/line, unlimited talk / text / data. Had it for seven years now. Can't beat that.

Every other year I will review my phone plan. I use Sim only plans because phones provided by carriers are generally awful in my opinion.

Never. I've only ever used a prepaid plan. I know exactly how much my bill is gonna be.

Well, not never. It's been probably 5 years since I got wifi and changed to the lowest Internet plan. Before that it was also years since my last change.

Not for 10 years. Sign up data plans looks so good until the cheap period is over. I got a good unlimited plan that I've been holding on for years.

I just switch providers, it's easier to get a good deal than by staying and nagging customer support. Though I currently pay €10,- with my current provider because I also have fibre with them, so I'll probably stay with them for the foreseeable future.

I switched ever couple of years.

Been with the same carrier 18 years now, same unlimited plan for at least the last 8.

I've got the same prepaid plan for over a decade, just sometimes buy more data.

Often, once a year or so. It's the only reliable way to get a lower price plan where I live. If I were to stay on the same plan I was on a couple years ago I would be paying an extra 20-30$ a month in fees for less data.

I have a prepaid plan that I never change. It costs nothing per month and I get 10 MB inclusive. I only add internet volume bundles when I need it for navigation for longer trips - to ensure it does not exceed that price (gets slower after).

After using some grandfathered T-Mobile family plan for over a decade I moved us to Tello. Still the same towers, but with our usage it's half the price.

Every other year or so, but only because there somehow keep being better deals. Over the last 8 years mint mobile has been consistently good pricing even for returning customers provided you're willing to pay for the whole year up front. That's my baseline. From there other small carriers come along offering unlimited for less and you join for a year or two until they go bust. Right now I'm on Spectrum mobile since it's free with even the cheapest home internet available to my address (for 12 months).

I think I've been on the same plan for about 10 years now. I'm with one of the only non-evil carriers in Canada, and I've never really felt like I needed more or wasn't getting my money's worth with them.

Whenever I change employer and they get used to my habits. My employers have paid my phone bill since 2012, so they pick whatever is cheapest for them.

Fun fact: Largest bill (so far) was ~4000 USD equivalent for one month

I do prepaid & get a new plan anually. It’s cheaper this way, less surprising bill-wise, & the rotation of numbers can help with security & privacy. All the carriers suck here equally but coverage is the same so I just see who is offering the best deal.

Every two years. That's how I get a new phone for free...

In the 15 years I've had a mobile phone I have changed around 5 times. But the last one was just an upgrade that added 40 GB of data while roaming in the EU, US and Canada to my previous unlimited plan for Switzerland only. That increased the cost from 20 to 25 Swiss Franks per month.

The answers here are interesting. If I don't change my mobile plan after it expires (2 years) and it gets renewed automatically it will get more expensive for the same service. Actually, if you want to keep getting a decent price, the best way is to completely change provider every 2 years.

Illimited message/phone calls + 110Gb here. Don't feel the need to call for 10 extra gb when i don't consume more than 50% of my plan per month.

I literally never have. Same prepaid thing for like 15-20 years. The terms have changed a fair bit over the years but I still only dump the bare minimum for long/no-expiry from the same provider. Averaged out it's only a few dollars a month.

It has some data now but I still just Wi-Fi hop in the rare situations I need internet.

Once a decade or so. Basically when they say "haha, your unlimited 3G plan won't support 4G speeds, upgrade to this more expensive plan that supports modern transfer rates".

Unlimited calls and SMS/MMS, 200GB data, lots of long distance calls covered: 16€EUR/mo. Why would I change ?

I've had the same plan for past 4 years. It's also my first plan I had.

Originally €12/month, but the price increased to €13/month. If I was to get it now, it would be €15/month. It's a data-only plan, but it gets me 300GB/month.
Unfortunately, my speeds are heavily crippled after shutdown of 3G. My carrier (Swan) only has 2G and 4G, but they had a contract with Orange for national roaming in their 2G and 3G networks. The FUP here was limited to 20GB, however in reality they allowed 40GB, as confirmed by the carrier (language: Slovak). The 3G offered far superior speeds during the day (30Mbps down as opposed to 1Mbps on 4G).

Last month however, Orange shut down 3G. There's now a new contract in place, allowing use of Orange's 4G network except the 800MHz band. So... what's the problem? It's not done in the way of "national roaming" anymore. Instead the phone signs into Orange's towers like native network. This also means I cannot explicitly use Orange's network anymore by selecting it in "Mobile networks" setting.
Apparently, this was done to allow for "smoother experience while switching networks".
I know a lot of people, including me, were using Orange's network for faster speeds like this.

But all hope is not lost, if you have MediaTek SoC, or a rooted Qualcomm device. For the latter, you should be able to use network signal guru.
For the former, *#*#3646633#*#* and head into band mode.
Here's the trick: The network is clearly set up to prefer cell towers owned by Swan, unless it is absolutely necessary to use Orange. But Swan only has towers in 1800MHz (B3) band. If you disallow that band, it is suddenly absolutely necessary to use one of the Orange's towers. Tada! Faster network speeds.
And also a warning: The carrier may not like you doing stuff like this. In fact, they may hate it, and ban you from using the network. There's not enough info whether that actually happens or not.

This kind of reminds me of an old PRL hacking article I've seen.
But anyway, it seems like these Orange towers may be doing some slight load balancing, as the speeds are now around 4-6Mbps during the day on home network. Still... 50Mbps on Orange towers.

Anyway, sorry, I got kind of off topic.
TL;DR: Never. My plan is cheap though slow. [Bunch of text] But it got a bit better.

I don’t. My carrier calls every time the exclusivity deal wears off to plead to renew it, and I just negotiate extra speed, higher caps on my mobile data or make the plan simply cheaper

For myself, my provider is online only so there's no need to call anyone. I end up just browsing the website once in a while or whenever I recommend them to someone. Beats having to hound a company and sit on hold forever when the online providers are what you see is what you get. Not to mention having to pay attention to contract expiry so your bill isn't randomly high one month.

I'm on the same pre-paid plan since 2005 or so.

Every 2 years. My 4gb data plan keeps going up in price every 2 years so I hop on to equivalent plans during Black Friday when the same plans are the rates I used to pay.

Did it a couple of times til I got a 10€ plan almost unlimited (186GB/month IIRC).

Ask for the Rio number and you get a good plan prolonged indefinitely, that was how it worked out for me anyways!

If you're in the US, switch to Mint.