I am really sorry to hear your system requires such an extended warmup. For tube equipment this is simply rediculous. I have owned a PrimaLuna integrated amp for over 10 years in my home office. I may have never discovered it’s sweet spot. I seldom have spent more that two or three hours in my office.
My main system is contemporary Audio Research Reference gear and my headphone system is Woo 300b… and neither have much of a warm up gain. In the past the Reference 5 series premps had a strange ~ 12 minute requirement to have signal passing through it until reaching optimal sound quality… it could be on for hours… but still had to have a signal going through it. This went away with the 6 series preamps. I don’t hear a noticeable improvement after the first couple minutes.
In decades prior, my equipment had a noticable improvement after 15 minutes or twenty… nothing like four hours.