Building 'Sticky' Members Areas?

So ive been brainstorming over the past few days trying to come up with some ideas to add inside some straight paysite members areas we're currently building out to make them more sticky so that members rebill longer and im not really coming up with anything exceptional that will work.

What do you folks have currently inside your members areas in addition to the content, to try and hold retention as high as possible?

We've tried message boards in the past but, members didnt really participate in them and eventually they just made the sites look 'dead' so thats not really a route im wanting to go, we've also added personal blogs for each members and whilst that worked for a little while, eventually they stopped being used as much as most members migrated over to Twitter.

So what else do you think there is that could be added to a paysite members area to increase retention rates that doesnt involve adding more content or updating even more than once every 24 hours?

Regards,

Lee