Originally Posted by
johnny99
Chain wear depends on a lot of factors, including how often you clean and lube your chain. Also your weight, power output, and the condition of your drivetrain. A worn cassette will wear your chain more quickly.
Good post. To that I'll add your riding style - whether you spin high or use low cadence as well as amount of steep hills.
To the OP, you should get much more milage than that. A 7 speed chain has wider plates than an 8/9/10 or 11 speeds.