I prefer annual or better fees for featured links. When I say better, I mean for more than 1 year. I offer featured (premium) links on my directory that stay in the top positions of the chosen category for 4 years at a time. Same price, they just stay featured for a 4 year period. I think it's more realistic than saying permanent, in fact my featured links sometimes live longer than the sites that were submitted. It also tells the submitter that me and my directory are committed for the long haul whether they are or they are not.