New wheels!

[Eden]

I have Velocity Deep V's on my rain bike - pretty well bomb proof as far as not going out of true if you run over pot holes and the like - but I did blow out a rim.... we had a really ugly winter for around here and they sanded the roads - that stuff just ground my rims right down and from what I understand Deep V's are a bit prone to side wall wear - since they are deeper that portion of the rim is weaker and can collapse easier.
I had already purchased a second pair before my first one blew out so I've been sticking with them - the original was used (came on my used TT bike) so I don't know how old it was in the first place and the winter here was nasty as far as road grit goes. Now I have one of the originals, two that are machine built Wheelsmith wheels and one that was hand built by my LBS. I'm afraid the hand built one probably did cost almost as much as the pair that I got from E-bay (and I didn't even have to buy a new hub...), but hey I did get a really good deal on those two - and I got two nice ultegra hubs on them.

[SadieKate]

Fredwina, why are you interested in the Deep V's? Eden races. She uses hers for a very different application. If you do some searching for custom wheels on the forums, you'll see that a lot of people long distance folks are using Velocity Aerohead OCs for strength and comfort combo. You might be sacrificing some comfort with that higher profile rim of the Deep V. My impression is that your goal is to ride 600k in one semi-consistent ride. Eden wants to ride as face as possible over much shorter courses.

Have you spoken directly to any wheelbuilders? If you need a recommendation, we have one in Fairfax that will ship anywhere. He just bought part ownership in Paradigm Cycles but also builds wheels under his own company, BFWG, which means exactly what you think it might. He made his name building for roadbears and he will talk your head off providing info about the choices. You will be a very well-informed consumer. The Deep Vs might be great for your application but be sure that rim profile will be optimum for your use.