All of the catalyzed primers shrink over time. Much less so than non-catalyzed primers, but they still shrink. Depending on the finish you are trying to achieve, waiting longer is generally better.
After spraying them out, allow the minimum recommended cure time at the correct recommended temperature and the shrinking is greatly reduced with these products, but there will still be potentially visible shrinkage after 6 months and longer especially if top-coated.
Most 2k that I have used develop a surface that must be sanded for the subsequent top coats to adhere to properly. An added benefit of this surfaces is that it helps block moisture from absorbing through the 2k prime coat over time.
Using the minimum thickness you can get away with will help greatly in minimize this. Using an electronic paint mill gauge can be helpful in guiding your sanding of the surface down to the point before you can see the underlying metal/surface.
