DVV, I've got a 100 watt Krell ksa-100,class A solid state . Gets REAL hot,enough to keep my audio room toasty in the winter,and warm in the summer! 
If you don't mind the heat, leave it on. Keeping solid state devices in a constant state, or in state of stasis, is always good for them. No cap discharge, no switch on surge, but the downside is the heat produced and of course, a heftier power bill.
But in terms of operation, you DEFINITELY have advantages: 1) practically speaking zero thermal runaway (since it's always heated up, there are no thermal changes), 2) lower distortion caused by thermal changes, typically down to the design limits, 3) easy negotiation of actual, real life loads straight out, as there is no time required for the amp to reach its nominal operating temperature, etc.
Plus greater longevity - life span is always increased when you run something in a more or less constant mode or regime. Even that of an automobile engine.
Cheers,
DVV
