At What Point is the Needle Damaging Records?

The needle is always damaging the records.

You should repoace the Stylus.
You could have the cartridge retipped. but it may cost more to do that than it is worth.
Get a new cartridge.

You are a little overdue, the damage might've been done already, hopefuly not.
Of course, the needle always damages records but let's not take this subject to the extreme.

Have you examined the stylus with a loop or magnifying glass. Perhaps you simply need to adjust VTF/VTA. I have my catridge (Transfiguration Temper W) more than 5 years and listen nearly as often as you do and highs are as sparkling as when I first installed it.

It may not be stylus wear but rather the suspension giving way. I don't know how to check that, but I agree with Stew, check the VTF/VTA first.