Yes. And I try to get them close to the same weight, too. The bike handles more consistently this way. I ride a CX bike with panniers when I commute, or go somewhere I need to lock up and leave the bike behind. I ride a carbon road racing bike the rest of the time. I don't like the fact that the CX bike already handles so much more poorly, and I want to keep the difference between the bikes to a minimum. Two balanced panniers helps a bit with that.