Hi Scott,
I ran the durahubs on both a single axle and a dual axle trailer. Both times I ran speedy sleeves just because I was being anal and wanted that nice smooth surface for them to run on. About 10 years of experience with them now.
For the single axle, the only time I ever had water get in was after I had the trailer sitting for nearly 10 months without using it. By the time I launched the inner seal had let out a bit of oil but I didn't notice until after the launch and got a bit of milky in it
For the dual axle I had a couple of minor problems. One was kind of self made. I had tightened the nut up after replacing the inner seals as a regular service type of thing and while it felt as tight as I wanted to go at the time, by the time I got home after the first trip where I got milk in one, I noticed it could have been a couple of notches tighter. The other one was when turning into the ramp as I back down sometimes one of the dual axles still has a bit of torque on the right rear or front left wheel. You can sometimes tell the torque is on the wheels if you see a bit of distortion in the side walls. I fixed that by getting the trailer nearly in the water then driving forward in a straight line then backing down straight and that seems to have fixed it.
FYI I got the plastic coated double lipped seals from my local bearing place. They are a little thinner than the metal ones but IMO do just as good a job as the mental ones and they don't rust.