First, the supplies that will probably need to be checked most frequently are the food and medicine.  Check to see what the expiration dates are for both kits and make a note to replace them when those dates occur.  If you have children, be sure to update their emergency clothing to the correct sizes as they grow.   Also check that none of the clothing has been moth eaten or become worn out.  Lastly, even if you think they are fine, do a cursory check of all your other emergency kits to make sure nothing has been tampered with or needs replacing.