Hardware damage from executing tight polling loop over extended periods of time?
There's nothing to save except battery charge (if your system even uses a battery). It will take just as much energy to delay() as it would to keep polling. The only way to save energy is to put the processor to sleep instead of delaying. And polling will be so brief that you might as well keep the sleep time short, too.

You probably don't need 10 uSec poll intervals; I should think your mouse would be plenty responsive with 1 mSec intervals. If polling takes, say, 100 uSec (and that's a total guess) and you sleep the processor for the other 900 uSec, you'll cut the energy use by 90%. If you don't need to save energy, it won't matter whether, or how long, you delay.

Update:


  "Does it make any difference at all, in terms of wear &amp; tear or stress
  placed on the CPU, how many loops I choose to make in one second? I'm
  considering something in the range 0.1Hz -> 100kHz Assuming that I
  keep heat under control and other vital parameters within their
  nominal operating levels, is it true that the frequency I choose won't
  make a bit of difference, one way or another?"


Yes, it is true. Your CPU can run full speed continuously, safely. It won't overheat from continuous running. Only if some part of your project is trying to draw too much current through the CPU; then that will cause heating, but the CPU polling a bunch of inputs is well within its specs.