I don't prewash.
There was a period of several years when many of the quilt managize I subscribed to only had one or two projects I liked, and many times even selecting ONE of real interest was pushing the boundaries. I copied those items in PDF format, and gave the INTACT magazines to our Freebies table at guild meetings. I do not share these patterns I copied. I didn't see any reason to cut up a magazine for a project or two, OR hto ang onto something solely to keep it intact while taking up valuable shelf space.