30 min warm up time is usually about right for my tube monoblocks and preamp. For the first one hundred hours or so I would leave it on continously and play music when you can. It will break in the fastest this way, but by then the electronics should be well settled in. If you're lucky you will get to be present when a break in "bloom" plateau appears; I recently had this happen with a new preamp and fortunately I had audiobuds over for a listening session when it happened. Everyone went "whoa!"
Tubes are amazing.
Tubes are amazing.