Would a heavy hand on the volume blow my 845s

I had the same urge years ago when I was driving an old Corvette. Some roads begged me to hit the accelerator. The speedometer went up up up. I eventually turned a bearing and had to have the engine rebuilt. It was an expensive mistake. Go with your instinct. If you think you're pushing your amp too hard, you probably are.

Warren,
I'm not familiar with your amp/speaker set-up, but here is a quote taken from an IAR review on an 845 tube based amp:
Regarding reaching the clipping point:
"Because the triode's transfer characteristic curves gently outside its linear region, there is no sudden onset of ugly sounding clipping. Instead, the sound simply starts becoming slightly dirty, grundgy, and fuzzy -- imperceptibly so at first, then gradually more and more noticeably as the music gets louder."
I would recommend that you contact tech support of your amp manufacturer for more info. The folks at Zu might be able to assist as well. Have fun and let 'er rip!

Yeah Stanley can have that effect... "Life is just a Game"(how about those drums Mr. Cobham!), "School Days", "Hot Fun", "Lopsy Lo", "Power", "Hello Jeff" you just want to keep turning it up. That's what 200 watt amps and JBL L-300's are for.

You cannot "blow" a tube with music, even if it is clipping. As Sherod said, "let 'er rip !".

Finally! Thanks 4est

Also, I may have this wrong, but with a SET, isn't the tube dissipating at maximum when there is NO signal, and is then modulated downward by the signal it is amplifying?