I wash my quilts with detergent, fabric softener and dry in the dryer. I use cold water and low heat.
I feed the wild birds and guess what gets on anything I would hang outside or lay outside to dry. A wet quilt hanging on a clothesline would put a lot of strain on the seams and quilting stitches.
I much prefer the dryer over the clothesline.
I don't expect my quilts to last forever.