I assume you refer to Jules Futterman designs which indeed sometimes did their contribution to heating the room. In any case, I ran a Graaf GM20 OTL for many years without even a valve blowing up, never mind the amp, before shifting to my Wavac. Generally leaving valve equipment on when it isn‘t being used seems ill-advised.
The reason why I am interested in getting commentary from users of the Allnic relates to its OTL/OCL design, which tends to be very wide bandwith and high speed, in other words: highly desirable for source components.