Missing members!

I've had my site up for about 6 months.  A couple weeks ago, I had about 113 members, and then it dropped instantly to about 90, but then they all came back the next day.  Now today, it has happened again;  I should have over 240 members, but it just dropped to only 103!  I'm assuming that they will automatically re-appear like the last time, but I'm wondering why this is happening and if there's something that I can do or if there's a setting that I can change.

By the way, I'm referring to total members from my Dashboard.  I know that this has nothing to do with DOB issues or anything like that.  These were all members that were here 30 minutes ago, but are now gone...

Thanks for the help.

Ryan

www.FreePersonalClassifieds.com

Go to admin area >> Settings >> Database Pruning  and set Clean old profiles by last log in ( days ) to 0

It won't remove old profiles.

By default it set 180 days - so it means profiles will be deleted in 180 days if noone uses it

Regards

Artur

Thanks Artur.  I actually already checked on that.  I had it set for 365 days, and the site's only been up for 6 months. 

All my members came back this morning, but I'm just confused as to how this happened.  It's almost as if my site reverted back to the way it was about a week ago; not only were members missing, but featured members that were made a week ago were back as featured, even though I changed them this week.  Either way, it automatically fixed itself over night, but I just want to minimize my site's downtime...