when is the recommended mileage to change a timing chain on on 2002 chevy cavalier

There is no scheduled interval for timing chain replacement. It is very rare to have timing chain break.

A timing chain is supposed to outlive the engine. should not need to ever replace

The Timing chain on the Chevy cavalier with the 2.2L EcoTec motor, is notorious for stretching and breaking, I've heard of them breaking as soon as 60k miles, and i've heard of them lasting longer than 300k. I would recommend changing it at 100k. Just to be safe, because these cars are notorious for having timing issues. If it has a timing issue, then it is only a matter of a few start ups, before you end up with pistons smashing your valves in.