If you're looking for something that will last a lifetime...these likely will not. However, I expect to get many years out of them. Some hold contents I access rarely, others are used often. I have one that holds my inhaler and chapstick on the outside of my hiking pack...very hot, very cold, LOTS of use on a recent trip (like 20x a day, literally)...I still expect this little bag to hold up for many years. Conversly, the one that holds my emergency 'things' in the car...I expect that one to hold up nearly a lifetime. They are plastic, no mesh, they are not "thick" but stronger than a zip lock baggy or even a Hefty brand freezer bag. I like them, the zippers seem well sewn for me and held up fine to my harsh use for the past few weeks. I am buying an additional set.