FWIW, the other day I replaced the serpentine belt on my 2015 TRD at 75K miles on the original .

Simple job. My tensioner bolt wrench is a bit long, so I had to remove the battery to gain the rotational leverage needed to remove and then replace the belt. Depending on what tool you use, this may not be necessary.

Other than that simple. Just make certain you have the belt routing diagram , as it is easy to route the belt over instead of under a roller , etc.

At 75K miles the original belt looked to be in new, perfect condition. I am confident the original belt would have been good for 100K miles. Just don't like the idea of messing with this job on the side of the road. I replaced it with another Toyota belt.

my original belt went about 150K miles and was replaced, it didn't break though - in all the toyota / lexus vehicles I've had or my family has had , never had a belt failure !