It's hard to say how many miles I put on my hubs before regreasing them as I have a couple of wheelsets that I switch around. I would guess I went about 4000 miles before I did it for the rear hub, but about half that in the front. I used these wheels mostly for commuting, but also for about two dozen very muddy cyclocross races in that time, so they saw some pretty nasty conditions. The original grease was still surprisingly clean. I probably could have gone longer.

Regarding the straight spokes, they make building the wheel a lot easier. Double-butted spokes are both lighter and stronger, but straight spokes will still give you a pretty good wheel. I say this as a very amateur wheel builder. I've built four wheels.