My work machine is an ASUS TUF GAMING A15. I don’t play any games on it at all. It was selected for me purely on its cost and performance as a development machine. I’ve had it for about 18 months.
The most worn keys are L, N, M, C, CTRL, DOWN-ARROW and RIGHT-ARROW. I wonder what this says about the tools and languages that I use or are the wear patterns more due to weaknesses in the plastics used to build the keys?
Not “worn” per-se, but I think I dropped it in my backpack and broke the q key [row 4 col 1], p [4 7], and the comma , [7 2], because the 3d-printed keycaps are quite delicate.
Fortunately, I was able to go to my local library that has a makerspace, send them the .stl file from my github, and print out some new ones for free! They’re the 2 white keys without any labels. The one marked Z on the top row is actually for the Fn layer, which is an oddball that I had lying around, so I swapped out the unmarked blue one which used to be there to replace the broken q which was more important to have the same shape as the others.
It was a lovely experience too. They were actually really impressed that I knew exactly what I was doing and only required minimal assistance.
At work, I have a cheap Dell keyboard, and the left CTRL, A, and S keys all went blank in about a year and a half. On my home laptop, the left CTRL’s scissor switch gave out completely after three and a half years, but none of the Thinkpad keys are worn out.
This topic was really enjoyable but alas, my keyboard is still nowhere near “worn” per se! Perhaps the most worn computer item I currently have is my mouse mat (cue purchasing a new one from the Swag Store 
This probably means a number of things…
Having said all that and in the spirit of staying on topic…my most used/worn keys are “command + enter” because its the quickest way to find things on my local machine.
My most worn is w,a,s,d and shift.
OK, I need to hear more about that keyboard. What is that layout? It looks quite narrow: is it for one-handed use?
It’s the… Bobbi layout 
I based it on the one-handed Dvorak layout:
I rearranged it so that it would fit in just 8 columns, both to minimize lateral finger movement, and make it super easy to design and build because it’s just a square.
Repo: GitHub - BTowersCoding/trochee: Parameterized ergonomic accessibility keyboard/computer
18 months is about the right longevity. The home row “locator bumps” get worn flat by that time, the letters disappear, my spacebar ends up having a valley worn into it.
Surprisingly, perhaps, is that my escape and backspace keys are usually pristine still, since I use CTRL-[ and CTRL-H keys for escape and backspace. The escape sequence gives me a chance to “stretch” my hands, even if a little bit, and nobody wants to travel that far to delete the character they just typed. (I am a VIM user, and I use spacebar as my leader key (because what else are you going to use it for?) and so does a lot for me as a key (pun intended) member of my daily activity.
I have to respond to that challenge! My leader is = (because whar are you going to use that for?), and as I was a pine/mutt user for a few years:
" for command mode, make <space> and '-' behave like pine, as pgdn and pgup
map <Space> <C-F>
map - <C-B>
The keys I’ve had to stick labels onto are:
R T Y U I O P S H K L : " C N M < >