You don't replace timing chains. Sometimes engines have a tensioner that can go bad and that get's replaced but I've never seen a chain stretch or break and need replacing or it being done as preventative maintenance.
The cost to replace a chain would be on par for an engine swap. It's not like a timing belt where it's easily accessible and should be done every 60, 90 or 105k miles.
Keep up on oil changes and enjoy your maintenance free, but slightly noisy compared to a belt, timing chain driven car.