I bought an adapter for my distortion pedal, since I wasn't sure how long the battery would last and didn't want to have to mess with batteries all the time. How often would you have to change the battery in a pedal assuming you had it on when playing your guitar - 2 hours a day for example?

I read somewhere (perhaps the instructions, can't remember) that you're not supposed to leave the pedal plugged in all the time - is that right? It's not too big of a deal to unplug it and whatnot, but its nicer being able to just flick my amp on and go when I want to play if theres no reason to keep unplugging it.

If I leave the battery in the pedal while using the AC adapter will the battery still drain? Or should it be good to go whenever I want to play without the adapter? Do you have to unhook the adapter from the pedal to get the battery to kick in (as opposed to just unplugging it)?

Finally I get some hum/buzz/hiss noise from my amp when the pedal is on - sometimes its quite loud other times not so much, I've moved it around to different rooms and tried turning other electronics off but haven't noticed anything obviously causing it to be loud or soft. I understand some noise is basically unavoidable though?
My Gear
Epi Les Paul
Roland Microcube
Boss DS-1 pedal
Shure SM57
M-Audio Fasttrack