When do you turn off the tubes?

I usually shut the amps off each time I am done listening.  Whenever I leave them on thinking I am going to go back to listening, my day usually changes so I can't.  If I turn them off, the odds of being able to listen more dramatically increases.  And, these things get hot-- including heating up the room when you have 8 kt120's per amp x 2, a couple of m8080's and a 6922 in the preamp, and the Sophia's in the CD power supply.  24 tubes total when everything is on-- that's too much electricity to waste if it's not in use.  And, finally, I have seen a tube fail-- right in my amp-- spectacular but scary.  I want to be around if/when that happens.

Less than 2 hours and I leave it on with the cd player on repeat with the volume turned down a bit. When I'm ready to listen I just turn it back up and put a record on...

The most potential damage to your tubes is turning on your amp. The likelihood of a tube exploding and torching your house are tiny. Some amps will pop a fuse if a tube flares and some don’t.  Bias type is most of the question there. I’d be more concerned with being electrocuted frankly. I would turn off after an hour or two of idle. But only once a day. No we regarding tube pre’s leave te=hem on in standby mode except when on vacation. They draw minimal power,the tubes last eons and they stay heated. But remember to pout in standby. Caps, etc go bad first from sitting and second from wear. If you are worried about tube replacement then you should, well...hey it’s part of maintenance. And I’ve been guilty of going out of town leaving a pair of monoblocks on—had to call a friend to go and turn them ooff for me. Fortunately he could get in through my garage with the code. Enjoy!

Same as most - off when done and 20min before to warm up ......

Just wondering about the 1-2 hour breaks.

We have a Standby feature on our amps. It keeps them lit but no B+ on the power tubes (the driver however still has B+ as the 6SN7s have a much longer life). This helps the amp keep its warmed up quality, but no wear on the power tubes.
But if I am away for much longer than that I just shut the amps off. If the amp has no standby feature I would just shut it off if you're only gone for 1-2 hours.