delete selective backups from Dropbox?

Hi 

I really appreciate the nightly backup to Dropbox feature - it is really important and gives good peace of mind.  Also the ability to restore from the backup through the automated webpage.

However now my Dropbox is getting a bit full, as is the computer that it's syncing to...  I need to free up some space, and I was wondering what kind of "schedule" people recommend and what are the pros and cons..   I'm thinking of keeping daily backup for the trailing 30 days, and then the first snapshot of each month previously.  

If anyone has a script (python or bash; I'm on Linux) that handles this kind of thing, or knows of such a tool, that would be great to know also!

Thanks

-Neal