How do I break in a tube amplifier?

To answer your question about playing music...yes .
Don't just turn it on and walk away , PLAY MUSIC !
Tubed equipment , as I have been told , need the electrical changes to aid in the break-in process .
I have not noticed a big change in electrical components resulting from break-in like I have from speakers .
And I agree about it taking @ 30 minutes to warm up for tubed equipment .
So if you only have short periods of time to listen ,tubes are the way to go . My SS phono stage needs at least 7 hours of on time for warm up and my SS amp even more .
Most people leave SS on continuously and turn tubes off when finished to save tube life .

Just another 2 cents worth .

With tubes there's a run-in period. At first, some tubes are not very quiet. With a few minutes they start sounding better and more quiet.

No offense to Polk432 but I thought it was funny how he mentioned 1001 precautions about tube amps and then closes with "Have fun. Tubes are great". LOL. This is why I went away from tubes.

The amp I'm getting has a soft start feature.

Any major issue connecting my receivers pre-outs to the tube integrated other than having two volume controls? I'm exploring options for not having to swap speaker cables back and forth as much.

Take the tape outs...cleaner.