In my experience component do need a period to stabilize. This can vary from one product to another and so can the results. Sometimes the change is quite sublte and each user can weight what value the process offers. I leave my digital front end gear on 24/7 as there is no "off" switch and was designed as such. The transport [by the same manufacturer] does have a power switch and is powered down when not in use. As mentioned, tube electronics react differently and I've noticed a more apparent benefit to warmup. Still, unless I'm auditioning or having friends over I'll just flip the switch and after 30 seconds I'm ready to go. Unless I'm using a slow startup rectifier like a Sylvania 5931 (5u4gb) which delays the current flow, leading to a softer start for the plate current flow of the other valves in the system. As they are conducting already when the rectifiers open up, the B+ and therefore the plate current raises slowly. My amp is a direct reactance drive - adjustable bias, zero feedback - 45 / 2a3 driven SET.

MikE