Change timing gear and chain?

I have an 02 Silverado K1500 5.3 engine w/190,000 miles and am needing to know is there a recommended time to change the chain and sprockets? I don't think I am having any problems yet and I want to keep it that way. What do you guys think? Anybody have one slip or go out on you yet? By the way, I am quit easy on the throttle on the truck and not much pulling at all. Thanks!

If it is not broke do not try to fix it.

I know it is not broke, but preventive maintenance is always a good thing. Why wait till it breaks? I just thought that someone had kind of an idea of about when to change it.