I bought this mattress cover last week when it was on sale for WAYDAYS so I haven't had it long and I haven't washed it yet.  I doubt I'll wash it more than once every 6 months bc It takes two people to put it on.  It entirely encases your mattress on all six sides.  That is to be desired, however, I'm unable to lift my mattress myself and pull the cover down as well.  It takes some effort, however, it DOES protect your mattress from moisture and bedbugs.  I also noted that it has a 10 year warranty by the manufacturer.