Probably sometime in 2013-2014 or so. I added a modified sign since I had the world on new years in 2012 but I didn't start adding signs until 2013.
When I run out of things to do or if a new worldgen-related update comes out, I'll fly out into new chunks and "start over" in a new area of the world. I pretty much always end up back at my spawn base after some time though. I've built a handful of smaller bases around the world this way. It's fun to explore and stumble upon things I built 5-10 years ago.
This is my very first single player Minecraft world started in 2011 that I still play to this day. I started adding signs in 2013.
As the drivers approach the board, an item box appears on G4
losing worlds it the worst.. I've lost some as well but thankfully not this one!
The world has traveled across ~4-5 different computers (and at least 2 countries). Currently I'm running it on a vanilla server on my local network so I can hop on with any of my machines and not worry about transferring the files.
I didn't start mapping until more recently so my maps are pretty underwhelming. Building a large map room is a project I haven't seriously considered before.. maybe I'll work on that next!
As for redstone, I have a decent number of automatons set up: some rail systems, plenty of original (and some copied) farm builds, some lighting and cosmetic things, potion crafting, etc..
As for food, I typically go for cooked pork chops because (1) have a ton of them already and (2) it fits the world theme well since they used to be the go-to when I started playing.