Oof. That's like the one lightbulb in the house that's been flickering for six months and you just get used to it, then one day it pops and you're standing in the dark wondering why you didn't change it last week. I've had a drill that sounded fine right up until the chuck decided to take a vacation and spin off into the bushes. Your mileage may vary, but in my experience if something's been making the same noise for a while, it's probably lying to you.