It's a lucky to be able practice so much. I can practice only about 8 hrs a week, so I change strings once per month or at least a two months. That is every 32-64 hrs of playing. Yeah, "ESP recommends that you change your strings at least every 20 hours of playing time", but that's realy too expensive for me)). So, it all is the reason to wipe the strings after each use, it realy prolongs life of the strings.