Susan, I understand what you are saying. I did lose a few tufts on the edge where there wasn't enough salt, and it was wet for the 3 months, and I've learned from that.
The neatsfoot oil compound states on the can that is is a preservative, and should be applied regularly.
Most of the books I have read say that they can be machine washed. I think it is long-term wetness that causes slippage, but I'll keep checking them.
Cheers, Bron.