I don't think it's stupid at all. If you buy a battery powered device and the manufacturer won't or can't tell you how long it will last, then for peace of mind change it after every use.
Or you could just sacrifice a couple batteries and do an actual battery runtime test It's the ONLY way to know for sure. For instance, my 9v LB lasts 18 hours on a single Energizer MAX 9v. Therefore, it lasts about 3 shows!!! I keep a small piece of painters tape on that 9v battery and after each show I write on the battery how many hours it's been used so far. So since doing that, I can EASILY record 3 shows with that single 9v battery
If 18 hours = 3 shows, you're going to some shows!
Well, you figure you get to show and setup around 8pm, and you teardown and leave around 2am, so thats 6 hours right there. Plus, if there are breaks between bands I just leave my LBs powered ON
I did 2 shows on my current 9v Energize MAX battery, and Ive only used up 11 hours, and thats being VERY CONSERVATIVE
So I have 7 hours left on my battery for the next show to record
I wish I could start using Rechargeable 9v NIMH Batteries, but Jon[Naiant] suggested thats not a good idea at all, because of their lower capacity and some othe technical stuff I didnt understand
I get 18 hours on my LB w/ my Schoeps caps because I run the LB on LOW power. When I run the 9v LB at HIGH power, I only get 6 hours, compared to the 18 hours I get on LOW power.
To the OP, Im sorry about the thread highjack, just wanted to make things clear