In addition to the ones tigerprawn suggested:
John Boultbee [Brooks]
I've found that Schoeller Dryskin and WB-400 fabrics are really tough and abrasion resistant. They are also nicely stretchy, and don't permanently stretch out the way woven cotton does. The caveat is that they make a huge range of fabrics, so I'd guess that the lighter fabrics with finer yarn will be more delicate. The Nomad shorts look to be a lighter fabric than my unkillable MEC jacket. And like any "refined" fabric (smooth yarns, even dyeing, smooth finish), they won't age as nicely as a more irregular natural fabric. The life of the shorts will likely depend more on your tolerance for visible wear, rather than complete destruction.
If you have a tailor who will handle this kind of thing, you could probably get them to make you a pair of shorts for not much more than the Nomads. If you've got a lifter's thighs and seat, bespoke shorts will fit you way better.
Not a stupid question. City dirt will kill the water repellancy of pretty much any tech fabric. So will mud and crap from actual outdoors outdoors usage, but I figure most SFers are city folk. Consistent abrasion from backpacks or whatever also wears away wp coating.
I use nikwax wash-in softshell proof, and tumble dry on low. Follow that with Grangers xt spray on proofing on the shoulders and hood. It smells rather chemically afterwards, but it goes away after a bit of airing out. Your jacket won't bead up like new, but it'll be way better than before.