It seems to me that the only way to do it is to ask each forum member to delete all PMs older than XX days.

I was thinking it would be easy at first, but mysql doesn't support what i was contemplating so it'd be more trouble than it'd be worth lol...

I was thinking after my first go failed (miserably) that you'd have to have a script that reads the pm's data and if it's older than a certain date it's purged; it could be made quite fast if all you take form the db is the id and the date (the date meerely to compare against, the date so you're deleting the right thing) then have an if/else statement to say "hey this is older than the date we have here, i'mma delete it"...

Not sure where all the differant portions of a pm linger, so i'd have to give it another looksie (keep in mind i'm from the .c family, so this is my first time really digging at a .t database).

You could set the pm limit to 50 and tell them all that they need to clean their boxes ...

That's a good idea, setting it to 50 or whatever and asking them to delete the excess.

Then they have the choice to choose which they want to keep ...