TouchID works great for a couple days, stops entirely after

When the iPhone 5s first came out, I couldn't get TouchID to work for more than a day. I blamed my job where I work with a lot of cardboard, maybe my hands are drying up and it's mis-reading my fingerprints?

With each new update, I would try it again, each time it work a little longer. I'm probably not allowed to talk much about iOS 8 here, but it definitely works best with that. I could maybe get around 5 days before it starts being unresponsive.

Would it make sense to bring this into the genius bar and have them look at it? There's no way I can really prove this is happening. I can't set up a fingerprint in front of them and show them it's not working on the spot. Also, would they do anything with the phone if iOS 8 is installed? I'm a registered developer, so its not that I'm not authorized to use it.

Thanks!