I repack mine every year cheap insurance. As someone else said it is a good time to check the brakes and tires as you have them off. I also carry one set of bearings with me when I am on the road. Once again cheap insurance and will save me a lot of "vacation" time and money if it happened, compared to finding someone to fix them, I am all about making sure my trips are as worry free as possible.
2012 Cedar Creek Silverback 29RE
2011 GMC 2500HD Diesel