If you are looking to ride xc, are you riding self contained or with a tour group? If you are going self contained, then I would look for something with 32 spokes and perhaps a Mavic or Velocity rim. Mavic wheels are very durable, however if you are in a small town, then there's a good chance that a shop might not have any of their spokes.... if they aren't a Mavic dealer then it will be hard to get replacements. I would be more concerned about durability then weight... if you should break a spoke on a light weight wheel, it affects a larger section of the wheel... and you could potentially be looking for a whole new wheel as opposed to a spoke.

AS someone who rides, tours, and is also a mechanic and wheel builder, my opinion is go for something with more spokes. I have been on the road as a mechanic in a small town, and was unable to find the correct spoke length.... If you insist on lightweight wheels, then carry extra spokes with you.