KLIM is an excellent company when it comes to warranty issues. We have sent many customers there way that have older gear etc that has started to peeter out. They do warranty things such as leaking, and issues with problems that could have been their fault during assembly. If it is ripped knees or obvious user inflicted issues, then that is where they draw the line for warranty, as it should be. But yes even if they are four years old they still will send ya a new pair, they just have to test them first, they wont just send out a new pair based on your word.
One thing you are gonna find out though, this late in the year is that if they warranty your pants, and they dont have your exact style they will either put you on a waiting list, or maybe offer you another version. And right now they are near sold out of everything in the pant department that wont be going discontinued or red-designed next year.
But a big thumbs up for sure for great service and warranty to our customers thus far!!