Hi Lappanion,
Try switching few of your least performing domains and 1-2 high performing domains to other parking program - Parked etc and keep it for same duration/
Again, depends on the quality and the priority of the keywords....
For my 500 indian domains, SEDO works good for some and Parked for others.
The rest 400+ TLDs, godaddy cashparking works fine for selecetd industry domains.
Try your luck playing around ... And remeber ... PARKING can never be a bread earning machine!