Let's say undergrad was 12 years ago.
I think it would be more then valid to make mention of a monumental opportunity that you took advantage of from back then; like a mission trip to Africa, for example.
If you attended high school < 8 years ago, I don't see anything wrong with making mention of activities from then, if you're just trying to flesh out your application. Again, only if they are monumental opportunities, and use them sparingly from HS days.
Just my thought...