I haven't used my amp in months or even years because I've been away at college. Now that I am home I am using it to record. It's a Marshall AVT 50, and has one 12AX7 tube in the preamp section. I have been turning on the amp everyday even if I don't intend on playing it. I put the gain on high to get a lot of juice flowing to the tube and leave it running for a few hours. Is this a "good" practice? or will it result in the tube life going down or even overheating and damaging it?