I wouldn't say "let" lol. For five years, I told her how much I wanted it. She slowly progressed from "It will never happen" to "Do you really want it?" to "OK, if I have an opportunity to and I want to, I will." Eventually, she made contact with an old friend of hers from school whom she'd never had any romance with. They began talking on the phone often, and I noticed she'd get flustered, and leave the room with the phone, talking quietly, etc. It was really turning me on.
Then she told me in an off-hand way that he had invited her to come visit him (in another state). I told her she should do it! "But," she objected, "If I go visit him, he will probably think we're going to have sex." "And why is that a problem?" Her eyes opened wide, as if she hadn't expected me to say that. lol
After asking me 100 different ways if I was sure about it, she agreed to go visit him. I had a blast helping her pick out what to wear for the visit. She would model what she would wear in the evening, which became increasingly provocative, finally getting to lingerie she said she'd wear for him. When I fucked her, she'd be intensely wet and horny.
She went to say with him for several days and would report back to me from time to time. Right up until the last night, nothing happened. She said they would go places and he would hold her hand, but never even tried to kiss her, and she decided it wasn't going to happen, asking me not to be disappointed. I said I wasn't, but I was disappointed of course.
The next morning, they day she'd be flying back home, he had left for work and she called me. We talked for a while about nothing, then she blurted out, "It happened." My mind had already accepted that it wasn't going to happen, so I didn't piece it together at first. "What happened?" "What you wanted to happen...it happened!"
My cock was instantly hard and I started jacking off immediately as she related the story of how they'd stayed up late talking and he started caressing her arm softly and suddenly she found herself hot and hungry for his sex. She reached over and grabbed his hard cock through his pants as they began undressing each other. By the time she told me about him sliding into her, I was on edge and shot my wad instantly. The only downside being that I had to wait another 10 hours or so before reclaiming her.