When you send your results to the archive server (see this FAQ) you take a snapshot of everything that is in your account so that it remains visible for posterity. Typically people do that at the beginning of the season, prior to doing a spring clean to remove old results and boats that are no longer relevant.
Several clubs have built up lengthy histories of results in the archives, going back many years. Until now the limit on the number of result sets each club could have on the archive server was ten, so they had to delete their oldest results in order to put the latest ones on. The good news is that I have increased the limit to twenty, so you can have up to twenty years of historical results available online, in addition to the current year.