It sounds like right now he has 18 months of not putting in much effort and six months of putting in effort. You appreciate the change but also, it sounds like, are not completely sure that you trust that it is for real.

An option would be to give things more to time clarify and for trust to grow. A year from now, for example, there would be 18 months of little effort and, hopefully, 18 months of more effort. Perhaps at that time you will be able to trust him considerably more than you can right now.