Another thing to keep in mind with chaps... they can tend to get soaked with oil, gas and who knows what over the years. (How many of us have forgotten to screw the caps on before picking up the saw at least once?) Oil and gas can degrade the protective fibers to the point where they provide little or no protection. Even dirt or other grit can abrade the fibers over time.
A 'Game of Logging' instructor told me one of his favorite stories about this: He was teaching a class, and verifying that everyone had the appropriate personal protective equipment. He came across one guy whose chaps were obviously well-used. No cuts in the fabric, but obviously had been the victim of a number of oil and gas spills, or leaky chainsaws set on top of them. He told the guy that they probably needed to be retired from chainsaw use. The owner disagreed, pointing out that they had no breaks in the fabric.
The instructor said "tell you what... I'd like to do a demonstration with your chaps that will certainly ruin them. When I'm done, if you can honestly say that you are happy with the protection your chaps would have given you, I'll buy you a new pair of your choice. If you agree that they didn't provide the kind of protection you were counting on, you buy your own chaps."
The owner agreed to the proposal. The instructor strapped the chaps to a tree, started up his chainsaw, and cut into the chaps. As expected, there was a huge mess of fibers. However, the saw managed to cut through quite a bit of them, and cut deeply into the tree before finally stopping. The owners comment: "Wow! Got a pair of chaps I can borrow for the class?"
