Haha! Excellent topic.
We're a two-bassists household, so we have a lot of bass gear!
I can often be seen going around the house dusting those basses that are on stands, as opposed to in cases. Sometimes I wipe them down with a damp cloth, if they're particularly grubby! I include fingerboards and the 'underside' of the strings. I have a large makeup brush (I don't 'do' makeup, anyway) to dust pickups, bridges and headstock tuners.
I keep an eye on the state of my basses' fingerboards and oil them when necessary, even if I'm not changing the strings. Same with cleaning the frets.
On the basses I use most, I regularly check action/truss rod, saddle height, nut height (on the Warwicks) and intonation. I have been known to be OCD enough to tighten a tuner's screw if that tuner is slightly looser than the others.
I have changed hardware on a couple of basses, and turned an electric upright from righty to lefty, but I don't feel confident enough to change pickups, or to do heavy duty cosmetic work such as sanding down the lacquer and changing the body colour.
I'm @Happy Jack's strings and general setup tech... 😎