Dont know the longevity of watch straps as I have many watches and wear them at infrequent intervals but I can tell you about leather as I'm into leather as well as watches and I've made belts, wallets, bags, watch straps, purses etc. There are many different kinds of leather with the most durable and hardest to cut being stingray which also is the most expensive. I dulled a blade cutting 1 watch strap then there is alligator, croco, caiman, buffalo, cow, pig etc. and there are many different ways of tanning the leather. Tanneries can tan the same leather and produce soft or hard leather, leather with a grain etc. Full grain leather is the whole thickness of the leather and is the best. Top grain is the top layer of the leather after it has been split to make it thinner and produces the top grain and suede then there are the various fakes starting with PU leather which utilizes the suede left over from making top grain leather. They basically coat the suede with polyurethane to make it look like leather. If you ever bought a cheap belt and after a month it cracked on the top layer this is what you have. The suede part will hold up but the PU part cracked. then there is leatherette and another form of leather where they take the scraps, grind them up and combine with a glue and I think they call this genuine leather. A leather watch strap that is sewn together would be made from top grain leather on top or alligator or whatever and on the bottom a softer, more comfortable leather such as pigskin. Pigskin can last many years, I have a shoe lined with pigskin that I have for about 20 yrs. I put 5-7km on it daily and its lasted.