How often do you balance your BFG ATs?

I was chasing a low-speed vibration on my truck, thinking it could have been my front diff, turns out all my tires were out of balance. I just had my tires rotated and balanced 3100 miles ago, so I was surprised that they were that far off. I didn't throw any weights, or at least I couldn't find any spots where weights once were.

LF off by 1oz
RF off by .75oz
LR off by 1.5oz
RR off by 1.5oz

How often do you have to balance your tires, And how much weight do you think is gone when you notice the tire is out of balance?

 

I rotate mine every 3k. It's not uncommon for a tire to become out of balance in that short a period of time. And 1.5oz may seem like a lot, but consider there's 16oz in a lb and your tires roughly weigh 55lbs.... I rotated my KM2's when I bought my Moto's (2.5k) and mine were out 1.75oz on 3 of the 4. Hope this information helps.