(Tongue in cheek)
I work for/with a non-profit, which uses donated computers. Video was "upgraded" to run 2.81a - end of the road for that hardware.
My personal laptop (weak) can't run anything past 2.81a.
Therefore, my "default production" version is still 2.81a.
My personal desktop can run anything. I came very late to the 2.9x party. I recently discovered that 3.0+OptiX works, so I started dabbling. (I loved Geometry Nodes, but since they have been redone it makes more sense to invest effort into the latest.) I guess if I create nice meshes I can use FBX to try porting backward.
Sometimes I get a little dizzy juggling versions. Does anyone else have the same experience?
I have 8 versions on my new desktop. I mostly use 3.1 and sometimes 3.0 or even 2.93 if things get buggy, but when I switch to an older version it takes me a few seconds (2.8+), up to a few minutes (pre- 2.8) to get used to the different version (some shortcuts might take longer to get used to...automatically use the new ones).
So no, I don't get dizzy, but I have been using blender almost every day for about 10 years now...
I got five versions: 2.75a, 2.79b, 2.80, 2.83 LTS, and 2.93. I've replaced 2.75a because I dislike the render process.
I just had installed 3.0 and I'm using it right until this year.
I am like Spikey, 7 or 8 I think.
Any new projects I start will be with the latest stable release, currently 3.0
then I stick with the same version through that project.
actually I just checked I have 9.
2.8, 2.81, 2.82, 2.83, 2.9, 2.91, 2.92, 2.93 and 3.0
on my old laptop I still have 2.78 and 2.79
I use the Steam version which is mostly the latest release. On my current project this has broken the packmaster add-on so I've reverted to 2.9(something).
So 2 versions installed here!
I still do have a copy of 2.79b for nostalgia/safekeeping, although I don't run it any more. It was my previous "production" version, for a long time - probably used for the majority of my projects.
Out of curiosity I checked my first crude project (that I know of) from summer 2012. It used 2.63, according to the .blend file.