Thank you very much.
If I give my jeans semi regular soaks/hand washing so the grime couldn't really build up could I get away with not really washing them (unless it smells obv, so I'm asking could I keep it from smelling). I manage all my other clothes by hand washing them a lot and they don't smell (just use hotter water or some manual agitation if necessary). I am really not a fan of the washing machine I guess. I imagine it should be fine just denim is a denser fabric so it's harder to get at dirt that's really penetrated the fabric.
I have a bottle of febreze in the cupboard, if i notice my jeans smelling a little I turn them inside out and give them a good spray and leave them to dry.
I have found that just soaking my jeans every 6-7 months is more then enough, although the colour of the water after a good hour soak is horrid. So washing more regular probably wouldn't hurt. I think it's a personal call, I've seen some fades on jeans that have turned out awesome and they have had quite a few washes.
If the jeans get messed up after a big night on the town or whatever just wash em. A soak for an hour won't hurt them, or just get a couple of pairs and rotate through them to prolong them.