This is like the 5th time I have bought for my husband and it's because he wears them out.  You can only wear them for so many years.  They are made of high quality material.  I noticed that he wears the knees out first.  Maybe they can reinforce the knee area???  That would be the only upgrade I would do to these overalls.  When he does wear out the knees I take them to my sewing machine and repair them and they are good to go for another few year.  Love Carhartt.  I guess that is why they have been around for so many years!.