Currently it seems that purged posts went from inception 1999 to aprox 2005, so in all likely hood most posters currently posting will not be affected, imho.
Of course that does not include Job who has been posting here since Jan 2000 and she will likely lose posts in the next purge.
We are only guessing that this might happen.
Currently we have Total Posts 1,812,327 that is a lot of posts.