Congrats. Under the silver hubcaps a dark brown would probably look fine. Often the built up brake dust looks brown anyway.
The longevity will be based upon prep and the conditions you expose them to, but something there is surely better than nothing. If anything, you might encounter some failure where the hubcaps friction fit in, but that's minimal surface area. For the cost and complexity, you can just touch up again.
If you wed to refinish your hubcaps, prep is probably a bit more straightforward, and you dns sand them more to get a bit more bite for the paint. Not sure how they would look brushed with a silver paint, but there are sprays that work and last pretty well...