I usually tweak stuff all the time. But I don't de-tune just to re-tune once a head is seated. I do find myself spending about 5 minutes dialing my kit into different rooms depending on where the gig is. I mess with my rack tom most, and my bass drum least. Snare gets a little turn halfway through a gig or after the second set. Whether its my ears adjusting (or losing hearing) I usually feel like I need to crank a little more tension on my snare by the third set.
My drums keep tuning well, but I always tweak them at every gig. Otherwise, for my home set, not too often to be honest, Sometimes I'll tune the snare on purpose, higher or lower, depending on my mood, same with the toms. But other than the occasional snare lug or high tom detuned lug, they pretty much stay where I put them. I'll bet a metal player has a different story to tell.
Once the snare head is seated, I hardly touch it (TIGHTSCREWS!) unless I want a different sound. If the head is played on for quite a while and the film stretches, then it's just a tweak or two to bring it back.
Toms--whenever my son gets done playing my kit...he loves to play on the rims. It does sound cool, but you have to bring a rod or two back up afterward!
I mainly re-tune at a show after the drums have been set up for a bit in the venue, just to get things even.
The bass drum stays pretty well set. I might have to turn a rod or two every once in a while if the hoops get handled a bit more than usual in and out of the case or something like that, but I really haven't had to do anything very often.
Before I practice, since my set is in my garage, and temperatures change a lot up here. (NorCal in the High Sierras) I even tune top and bottom heads, as during some tunes I beat the living hell out of everything, and I can hear the difference when playing softer, more "finessed" songs.
I always tune after setting up at a gig, and check again after the 2nd set.
I have cheapo heads on my rack toms, and those seem to need the most attention. Those are also the heads I've "ironed" the most.(go figger!)
Bass and snare generally set it and forget it, I usually change heads every six months unless i'm starting a new recording session. They're usually fine for the duration. Toms i usually have to tune once a month or so to ensure the intervals between the fundamental is where i want them to be.
I tune tom batters at every gig, bass drum maybe once a month. I only mess with the resos if things are really off or there is an unmusical ringing tone. I re-tune batters after I put the mics on also.
My snare gets tuned every gig top and bottom and sometimes between sets and even between songs. If i'm cracking alot of rimshots the screws will come loose. I'm constantly fiddling with my reso head to get the right sound and to try to minimize sympathetic buzz and it's different every show becuase of different monitor set ups and different stage layouts.
I take everything apart about once a month and change out heads and do a full tuning of everything. I change resos every 4 months on toms maybe every 8 months on snares and hardly ever on the bass drum reso. It might seem excessive but I do gig ALOT. 20 shows a month usually and 4 hour shows each night.
I typicaly play every day, and will tweak my heads every time I play.
For studio stuff, I tend to have fresh heads on every time, and will re-tune as needed. I have had to change snare heads up to 5 times for one record.
For live, I will have a fresh snare head for every show, Toms I'll let go make 3-4 gigs. But I re-tune both the batter and reso for every show.