I have had the following class D amps in my system over the years: Bel Canto REF500 and REF1000 Mk.2. Rowland M312 and M925. In all cases, I have left them on 24/7 while monitoring the local wheather like a hawk. Whenever thunderstorms are in the forecast for the day, I always turn off the entire system and unplug each component from the AC outlets.
BTW, with all amps that I used in my system, class D and A/B alike, I have experience that the audible behavior is maximized if left on for about 24 hours while generating some kind of low volume sound... I usually connect an old FM tuner set to interstation hash.
Class A/B amps have included Aragon 4004, Rowland M7, Rowland M625, Rowland M725. All benefited from being at full power 24/7... Invariably took 24 hours for any amp to run at its sweetest. It was possible to run M625 and 725 24/7.... Tried that on the old M7: costed me $150 of AC over a two weeks stretch *Grins!*
BTW, I have never experienced an SMPS giving up on me.... All have been rock solid.