How do I break in a tube amplifier?

I should be taking delivery of my Yaqin MC-30L tube amplifier this weekend. I believe the dealer is going to set it up and bias it and may even let it run for a few hours before I pick it up. It's going to be a 2nd system sharing speakers with my primary home theater system so I will have few opportunities to leave it running for extended periods of time.

Does it do any good to just leave the amplifier turned on or does it actually need to by playing music?