Many years ago the third chain I installed on my 6500 cassette started skipping almost immediately upon installation. I think it may have been the 3rd or 4th gear but I can't remember for sure. I thought maybe I could ride it out into shape but that didn't work. So I changed the cassette and skipping continued. So I put on a new chain and all was well. I think I ruined the barely used third chain by running it out a worn out cassette. My rule of thumb after that was two chains for each cassette. I know there are people who post about getting extraordinary miles on their drive-train but I'm pretty skeptical. I ride in good conditions and have always been pretty fastidious about cleaning. Generally I change a chain between 2,000-2,500 miles (I've not noticed faster wear on my 10 and 11 speed bikes btw), so I do think that changing a chain at 1,500 miles as the poster did seems a little quick--but then again I don't know that conditions he riding in. It's a wear part(s) and I'm actually fairly happy I've been able to ride enough to need to replace them.