Hurricane Owners - Biasing Question

I have been running the latest iteration of the ASL Huricane tube monoblocks (w/ the green PIO caps, triode switch, stronger chassis, upgraded parts, and new biasing system(??))over the last few months, and it seems that I'm spending an awful lot of time re-biasing the power tubes. I'm wondering if I'm just being too anal with the biasing, or if there is a better method or strategy to this madness.

When I start the amps up, the bias current starts low (low to mid 400s) then work their way up to over 500 over the course of a half hour or so. Over the next hour, they will drift down to the correct bias of 480. They stay there for a while, especially if I continously play music through them. If no music plays, then continue to drop to the 450s, or if music is playing, it takes a few hours to get down that low. So I find myself tweaking down when they're over 500, then I'm tweaking back up to 480 when they drop below 470, etc. etc. etc...Then at the next start up, the biasing is all wrong, and the cycle starts again. BTW, the tubes (KT88-EHs)are all burned in.

Is this normal (hey, this is the first time I've owned tube amps...)? What is the net effect if the bias drops too low (less power output?, sonic quality?) or of bias goes too high (reduced life?, sonics?).

Anyways, I think these are great amps despite the continuos fiddling around with the bias, and I'm enjoying them immensely!

Thanks....