Some wild advice in here. Look at how often guitar players change their strings, sure, they tune up fine but after a while they start to sound really dull. just like drum heads.
I do it about 2 times a year, mainly because I can't afford to do it more often. Touring drummers sometimes do it every few gigs. So keep that in mind, but they also are not paying for it.
The issue is that it happens slowly when they wear out so you don't really notice it, until you change them. Then it is night and day.
The bottom or reso heads matter just as much as the top, maybe even more. I see guys who just keep changing the tops and wonder why their drums sound dead.
A good rule of thumb is if they are dented, change em. If they sound dead, try tuning them, if it is not working, change em. If it has been a long time and they don't sound good, try and tune them, if it isn't working, change them. If your bored and want something to do, change em.
But at the same time if they sound good, just leave them.
2 times I change mine are right before I go into a studio to record, and when I want to switch from coated to clear, single to dual ply etc. I usually take off my old heads and put em on my second practice kit as they still work.
I also change my snare WAY more than my toms, every month or so as it gets hit probibly 50x as much.