Anna, thanks for making that change
In the ccbill admin area you have the ability to disable rebills for individuals or for all affiliates. If you enable rebills now and then disable them a few months down the track, the change will apply to everyone, not just new affiliates.
When it comes to attracting affiliates, you need to offer them incentives to send you their traffic, especially when they could be sending it to the monster companies and getting $35 a sale or whatever. So only getting $7.50 for a signup and no possible rebills is a disincentive.
But I think your site is fab, it has lots of indie cred and your niche isn't saturated so I'm glad you're going with the rebills now.