honestly, everyone sweats/smells differently.
i personally don't sweat at ALL, unless of course im working out/exercising of some sort. and if you're wearing your jeans properly/take care of them, they last me about 10 wears or so. and believe me, they still smell fresh, or else i wouldnt wear them that long. and besides, when you spend ~200 on a nice pair of jeans you want them to keep color and stay new, so you wouldnt want to wash them too much. (and its great advice to turn them inside out when you do wash them). if you sweat a lot then of course you would have to wash them more often.