Delete old sms messages

[resarfekim]

I've accumulated a couple years worth of SMS/MMS., that I always backup/restore with Titanium when switching roms.

I'd like to delete all messages in all threads except for the most recent 20 per thread. There is a Delete Old Messages option in the SMS app, but it doesn't work. (I'm on the new Lolipop rom). Anybody know how i might truncate my messages?

Thanks!