Other than some low dips and valley's, the trails I ride seem to drain quite well, not to mention the area does not have a ton of big hills, so I never really see errosion problems. The trails all seem to stay in great condition. If there is a section that has dried up with ruts, I don't really see the issue of just riding them. I think it just sharpens skills if anything. But I repeat "sections". It's not like a whole ride is a continuous rutted up trail. But in agreement with skiahh, soil would make a difference.