We get our yurts and lotus belles professionally washed proofed and dried each year. Costs us about £1000 for all 4 of them but extends the life by many seasons. The biggest issue we have is with drying everything in October. The lotus belle can put up in the barn if I take everything out but the yurt is too big. Last year, we had to wait three weeks for enough dry weather just to take everything out and take them down and they ended up with mildew and moss growing on them.