Every program with have at least one or two members that stick around for a LONG time. It doesn't mean they like the content or that the members are even still alive. It's just something that happens. Asking the retention of the average member might be more useful
Don't you have other webmasters to confide in for a question like this? You'll just get loads of worthless information on here from sponsors and sig whore (i.e. bullshit)