I have bead blasted and powder coated my original wagon wheels as well. One of the problems with OEM wagon wheels is that they are two-piece welded together, rust likes to permeate through where the two pieces meet and is hard to get powder or paint into the crevices. I spent a considerable amount of time blasting each wheel in those areas so all rust would be eliminated before powdering.
After powdering, I used a body sealant in the cracks that I removed a year later because of discoloring. Now I just push paste wax in the crevices every year and have no signs of rust. You gotta do what you gotta do to keep water out in those areas because it is very difficult to get powder to flow into those tight crevices to begin with. Paint or powder, the results will be the same. Just keep it waxed but I know a lot of people will not take the time to do so, it is evident when you see chrome center caps on how pitted they become because no one bothers to wax them either. I do, and my originals always look brand new simply because they are waxed every time I take my wheels off for rotation.
If you want something to look nice years from now, you simply need to spend the time to keeping it cleaned and waxed.... period!