Inspect every 30k or 2 years. If it needs to be replaced, replace it. If it looks good, run with it.

I would like to think the belt would show wear before the tensioner shows excessive stretch.

I inspect mine every time I change the oil. '01 w/ 70k. Original belt.

 

Just changed mine a couple of weeks ago, no biggie just remember how it snaked around. Mine was slipping at WOT on upshifts for a while (since 25k?) but hasn't done it since w/ the new oem: 38920-pcx-004 for '02, $91 list, 70 over the counter here in NY.

 

FYI check that the pulley operation is smooth. My bearing was going bad so I replaced it along with the belt.