How hot is hot when moving from class a/b to to a or tubes?

Define your description of what is "hot" to you?.  

I'm re-evaluating this myself again recently. May be helpful to compare w/others.

SS: My full-on Class A 50w solid state amp is said to be operating normally when you can hold your hand on the side heat sinks for about a max of "ten seconds", reasonably. Confirmed by the original designer and recent tech who performed checks and upgrades.  Special grease was added to the OPTs for maximum heat transfer to heat sinks, @47-50c temp max, and recently biased up and upgraded.

TUBE: my two mono block tube amps run two KT150 or two KT120 output tubes per amp. Can hold a hand on the transformers for ~30-45 seconds no issue. Toasty warm but not what others might consider "hot". Will recheck actual temp with infrared laser next wk after re-biasing tubes to their max to see what max heat is. I'd expect higher power 211, 845 triode amps to run a bit hotter in full Class-A.  

@decooney 

i kept the hot question vague for the reason you describe - want to get a gauge on how others articulate it. My main concerns were: potential burns to the kids (probably their friends. Thanks @jonwolfpell for the cage comment), how much it will heat my already hot home, anyone speaking about shutdown modes from over heating (there are few Texas folks running them in the summer, the UK won’t be hitting those temperatures), hopefully getting some insight on what experienced owners would do if they were starting out again. 

I’ve never owned tubes so I have too many unknowns. 
My next stage will to start home demos and take it from there. 

A lot of the tube amplifiers mentioned in this thread are much more power than you need.  2 wpc will be enough unless you like concert volumes.  A 2 wpc tube amp will be almost no heat.

Also, my comments above are made without air conditioning.  I live on the california coast and don't have air conditioning.

Jerry

@carlsbad i hear you there. I will be looking at single digit wpc. 
very excited for the next steps. 

@mpoll1 My main concerns were: potential burns to the kids (probably their friends.

Two added points of information have surfaced here. And, if you plan to keep your nice L509x amp and rotate in a tube amp once in a while, going a new/lower power direction will be key for less heat and you can also look at integrated tube amps with an enclosure. Do you want to stare at tubes or keep them enclosed, separates or integrated all-in-one unit?

While some will push for the fleawatt single-ended-triode tube amps down in the 2-3 watt range, there are also some very nice EL84 based tube amps in the 20w range that can be nice too. Thinking if you want something [enclosed], we can also make a plug for this one, makes it nice for those starting out with tubes. Here is another to give ideas. Some used ones out there right now too. Another option, fwiw.