50/50. Mostly on longer rides. I personally hate having anything in my ears. Sometimes I use only one. It cuts some of the noise and limits the low frequency sounds.
Huh...what? Just kidding! When I'm scooting around town I don't use them. But when I'm riding long distance or up in the twisties I ride with foam ear plugs...I think they're best at noise muffling IMO.
I have used ear plugs for years, it really does cut down on the fatigue. For my Nashville trip (which I'm still on), I bought some custom molded earbud things, made and sold by "Decibullz". Found on everybody's favorite auction site for $18.00 shipped, you mold them to your ears and install your own earbuds. They are so comfortable that I can't even feel them. Cuts the wind noise by a boatload and I don't have to blast the music to hear it.
I use ear plugs on rides over 30 miles, the only thing special about 30 miles is that is how far I am from Boardtracker Harly and I ride there without them. I agree they can be uncomfortable after awhile, I use cheap foam ones from Lowes.