Timing Chain---When?
 

I have a 2000 Boxter with 74,000 miles on it and can find no info online on when to change them. I know what the dealer will tell me and was just trying to verify the time limit on these things. Please inform me.

It should last until your engine needs a complete rebuild -- figure anywhere from 150,000 to 300,000 miles depending on maintenance and how gently you use your car.

You're most likely referring to the Drive Belt rather then the 2 timing chains (1 for each cylinder bank). It's the only thing requiring regular maintenance.

This should be changed at least every 60k mi. or 5 yrs. whichever is 1st. Easy DIY procedure, the belt costs about $25-$30.