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

The only time mine are off is during a power outage. 

I unplug my system when leaving for weeks...and I do believe it sounds better when left on...

My system is on all the time. Like markalarsen, the only time the system is off is if the power goes out. 

I don't know about others out there in Audioland but when the power unexpectedly shuts down and then starts up (could be a second or could be much longer) it effects my tube gear and turns them on. I don't want my tube gear on when I'm not listening or at home.

How can you be sure an amplifier really does sound better when left on? Human sonic memory is not more than a few seconds, so you can only know if you compare two identical amplifiers, one left on for a while, and the other started from cold. To be honest, if there really is a difference (which in most cases I doubt), it would be a bad design.
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.