Cheap-ish chain and cassette (10 speed SLX/XT or equivalent), replace everything when the shifting reaches the point of 2 down one up (c.a 2000miles).
Having two or three working bikes means I just grab the SS or touring bike, and leave the racer or nice MTB in the shed if it’s going to be horrible so the more expensive drive chains last far longer anyway.
I tried rotating chains, but it seems that 90% of the wear occurs on those rides where the lube washes off, so one chain was always far worse than the others anyway after one of those rides, and putoline means this happens far less often these days anyway. I suppose I could rotate the chain when the wax washes out, but then with three chains it’d probably only need doing once in a year (and keeping track of 3x chains, on 4 bikes is going to get faffy and probably mean 13 speed will be out before they’re worn!).