I have been down this road. It's a sliippery slope. I felt the more I wanted to limit the time, the more of a battle I had to contend with at home. What finally worked for us was every other day, and I helped him coordinate an activity--watch a movie in the back yard, ice skating, board games, a TV series party. He realized that with a day in between to plan, he could really come up with something nice that made their time together more quality. It gave them something to look forward to. We set a curfew. If there were times we were doing a family activity, we would occassionally ask if he would like to invite his girlfriend. For us it came down to, "Let's take this dating thing to a whole new level. I have some thoughts you might like.." and we sat down and I talked to him about ideas for dating...for the movie night, we prepared together by making pizza dough, preparing snacks and setting up the back yard with the projector. It was time I loved spending with him and he was still able to do something "for her" without being "with her".