Is there any danger in leaving a class D amp on unattended for ten days?

Class D amps should idle at a lower level, so that should be OK.
Being worried about fire is a real issue and i applaud people for being careful. I designed a bunch of stuff for various companies, two my own, in the 80s and 90s and the careless stuff i saw in the field scared me.

That said, since i still design and therefore experiment, i leave stuff on while I'm away all the time.  I don't leave amps on flammable carpets, i leave them some kind of fire retardant stand. It can even be wood - you wont have an inferno - just maybe a spark or 40.

Disconnect the speakers. No need for them to sacrifice their lives to a turn-on-off transient, or lightning, or .....

They should be fused such that most bad conditions just blow the fuse.  I personally under-fuse everything; i want the $1 fuse to protect the $3k amp, not the other way around.

use common sense.

G

"Apart from the two disadvantages I already mentioned (fire risk and harm to the environment) there is of course another one: heat is the enemy of electronics. Leave your gear on and you will significantly reduce the life span of critical components. "

Not true. I design a lot of this gear, and the turn-on/turn off shock is the most likely time to see a failure -- or when its induced by, say, lightning.  Any well designed equipment is designed to work well below its thermal, voltage and current maximums.  The major effect i see  over long periods ( and remember, i see significant numbers in aggregate) is the deterioration of electrolytic capacitors. This *may* be accelerated byt he very modest temperatures we're talking about, but its mostly just the drying effect of age.

The constant heat also has a beneficial effect: it keeps things dry and free of mold.  I've seen more failures due to moisture and mold then heat.  Of course that's not dramatic since the hear related failures i have seen is, roughly, well, zero.

I turn stuff off to save money and the environment, and since a storm and a turn on/off thump might be unpleasant to speakers. But not due to the fact that they might be at 40-45degC.  Yea, the heats sinks on a class AB amp might get hotter, but the only thing attached to them are transistors rated to 185C.