Makes sense for Perry to stay in at least through SC. He can make a few appearances in NH and do all the debates before NH & SC. Run a few ads in NH and a lot of ads in SC, do all the rallys he can in SC and see if he can improve his image and his standing with the voters.
I think Perry wants the VP slot, and making a strong showing in SC, will help improve his position. I think a Santorum/Perry ticket would be a pretty strong ticket.