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

"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.

My 3116 chip amp hasn't been off since I set the system up, but it's probably more prudent to turn everything off if you're going to be away.

I would not leave electronics ’on’ unattended without power condtioning. Who knows what might happen if the power goes out. High frequecy noise spikes could damage your system becaue it is digital not unlike a computer. A legacy power amp would be less susceptible. It is not worth the risk of component failure burning your place to the ground which could happen
   My recommendation? Turn on the system 15 minutes before listening and have a cup of tea or coffee. Relax.

Whenever we go on vacation I turn my audio equipment "off", and since my system has a 1500 VA APC battery backup/UPS between it and my wall outlet, I don't "unplug" the units, as I once had a bad experience with the firmware in my preamp getting corrupted (source of that problem unknown), and all my equipment together consumes less than 10 watts connected, but turned "off".