the good thing nowadays is that (around here anyways) there are so many more options for buying panniers. Like all diy projects, some are perfectly fine and as good as anything you can buy. Other things sometimes are a balance of cost vs problems or even like I mentioned, a prob that could result in a cost of a repair. But again, depends on how much you use something and how well made it is (bought or diy) to know how much to spend. As I commute a lot, its worth it to me to have a no brainer system that I never have to think about, and over all the years owning stuff, it ends up being cheap in the long run.
Have fun making the new set.