You could need to change your chain every 500 miles, but it is improbable. Get a measuring gauge, Park Tools make a good one, and keep an "eye on it". I change mine anywhere from 1,000 to 2,000 miles, some bikes I ride harder, some I ride dirtier.

Keep your drivetrain clean- your parts will last longer and shifting will be faster and more accurate.

Ride Far
Pat