I have had my rails sitting in my garage waiting to be installed for over a year now. I'm sure they have held up great but I was more concerned with rust/corrosion. Any problems with that aspect yet?
The set I have is made by Mac's Tie Down's, but is the same basic concept and also an aluminum rail with stainless hardware, and it has held up fine. From what I have heard the powdercoat wil flake off eventually if that is on the version that you chose from the company in the original post. But regardless, the rails really shouldn't rust easily being that they are aluminum. Worst case just coat them in Fluid Film.
The system is great though, especially for tying a tire or jack or whatever else down while offroad, but is also nice and versatile for every-day tasks as well. I like it a a lot and may eventually add some panels on the sides as well.
The install is kinda tricky though and obviously requires two people. Also, my recommendation is to do what others have said and just get 4 longer screws and drill completely through the hat channels for extra support as well as making the job so much easier.