I've read a few ride reports on AdvRider.com from WR250R owners who would have problems with their fork seals leaking. The way it was explained to me is that dirt gets past the wipers and under the seals, then the up/down movement of the forks will slowly eat away at the seals and cause them to leak. To prevent that, I installed a pair of Seal Savers which will keep dirt and mud from getting up in there and causing problems. They are made out of neoprene so they should be durable, and it won't hurt to get them wet. I got the ones for inverted forks with 1 3/4" diameter (44 - 50mm) fork tube.
Unless you get real creative, you do have to remove the fork tubes to install these, but I figured that would be better than having my fork seals start leaking in the middle of a long trip.
Where To Buy:
• Seal Savers at SoloRacer.com