Timing Chain replacement

The Scion XB has a timing chain. I haven't seen any problems with them, two customers have 100,000 to 130,000 miles on theirs no problems at all.

No, you don't. Timing chains are not regular maintenance items, and they don't need to be replaced unless there is a repair that needs to be happens. Check your owner's manual. If you have a timing belt, and not a chain, it will need to be replaced at an interval defined by the manufacturer.

I have one customer with 190,000 on the same chain with no problems, not a wear item unless abused.