You can actually download it on 5 different profiles, so if he deletes em and redownloads em on the same account he won't lose any of those 5. It's only if he gets another playstation and downloads em without deactivating the old one that he'll lose a credit.
My recommendation would be to just buy a 120gig hdd and chuck that in, you can backup all your data if you have a USB harddrive using the backup feature. Getting a larger HDD will also help prepare your PS3 for the PVR attachment later this year.