My New Dorm Room... My Trucks...
I think the manual says to rotate every other oil change, and to balance every other rotation.
I say to balance and rotate about every 5,000 to 7500 miles. 10k tops, or basically anytime you feel vibration in the wheel that is not RPM related, but MPH/speed related. Trouble is after a rotation, you could have a vibration problem you never felt because the rear isolated the balance problem, but when they are now on your front wheels, it can be felt.
Basic logic says that if you're gonna pay someone to take them off, might as well pay a few extra bucks and have them balance them too.