I always enjoyed the process of hearing things open up- I'd say 45 minutes is sufficient for the Lamm ML2 SETs and a couple or three sides of LP for the cartridge to really come into its own (after initial settle in which could vary depending on cartridge). My small vintage system running old Quad IIs with period glass (GEC KT 66s!) and restored Quad 57s is pretty much the same on warm up time. And you can clearly hear when these systems just bloom- everything opens up.
I've been using various tube amps and preamps since the early '70s and can't say my experience decades ago is much different using then current ARC tube gear, but my sonic memory isn't that good.