In my main system, 45 minutes to warm up a pair of Lamm ML2s with a fresh tube complement. I usually do that with a digital source. It takes about 3 sides to warm up the tube phono stage and cartridge. I can make the time coincide, but that's the reality.
A different tube system, running a restored pair of Quad '57s and Quad II amps using GEC KT 66s (real ones) takes at least 20 minutes to come on song, more time is better. The speakers are on constant charge.