Happily, BoonEx has announced they have "fixed this" in the Dolphin 7.0.2 release.

default database pruning settings (180 days)
So new installs should not suffer from this problem... but if you have an install prior to Dolphin 7.0.2 (or even if you have upgraded to 7.0.2 from an earlier release), you should double check these values... so you don't loose your hard earned users!

Smoge