I ride either on beaches (mix of sand and gravel) or sandy / muddy sand forest trails. I’ve not had a problem with drivetrain longevity, in fact the current SRAM chain, specialised chainring and sunrace cassette 1 x 10 setup on my spesh fatboy are still going since last November despite average twice a week use in those conditions.
I’m not fastidious about cleaning either, but do give the bike a rinse off after beach rides, and always use Finish Line wet lube – which does attract crap sometimes but seems to do the job.
What didnt last though was the crap specialised BB and hubs. all replaced with Hope now for hope-fully better durability (excuse crap pun).