One person’s bad experiences don’t necessarily apply to everyone.
chinpo - Use the search button, top right of every page, and click the “advanced search” link. On that page enter “permanent” as the search term and use the pull down menu below the search term box and select “titles only.” You’ll get a list of past threads where people have asked this same question.
Basically it does last, but many have to do a “maintenance” routine once a week or so to keep it. If you just stop, it some of your gains will be lost. See this thread by supersizeit regarding his loss after stopping PE.