I've always had A policy of mutual regret policy. with no time limit. The deal is: that on mutual territory we meet with negs in hand and a pair of scissors. Prior to this meeting they are aloud to choose their favorite few images that are printed and handed to them on an agreed to price. then cut the negative to pieces. you should prior to this go thru the work and choose you educational favorites and make prints for a referral file towards future plans on your images. These images are reference only. If this guy harasses to much don't be afraid to file a police report. and have witnesses at the shredding. I had this happen one time with a hair stylist who asked to model for me then her coked out boyfriend came and threatened my wife and I till I gave him the negs. (pervert) so I called the police they took him out of the studio and she and I shredded the negs. Never heard from them again. The 2 other times I had models who regretted their experience it was done in a friendly way we worked through it together then cut the negs. Giving your negs away is a bad idea if they ever do get published out of your control you could be in a lot more trouble. If you do photograph anyone nude again state up front that if do change their mind don't hesitate to call. You can always re-shoot with someone else.