I'd planned on waiting at least a few weeks. I'd had several partners who I finally gave in and slept with, only for them to lose interest because they'd gotten what they'd wanted.
Of course, I didn't count on connecting/clicking so powerfully that we drove each other wild. Even HE wanted to wait, because he was technically a virgin. But we ended up having sex (just over) a week into our relationship. Before we started dating, we'd known each other for 6 years, so I don't feel too bad about it.