DO I LEAVE OR DO I STAY??? Ten years in and we spend less time together than we did at the start!

I have been with my partner for nearly 10 years. We both have teenage children and live apart but have seen each other every 2nd week. Over the last 12 months we have been seeing each other less and less as he wants more time to himself. So the week we used to spend together is now only 1 day on the weekend and about 3 nights during the week. I always thought as the kids got older we would start to spend more time together. I have never asked for a ring on my finger but I do want some sort of commitment that he wants to be with me for the long haul. Over the years I have suggested holidays and things we should do in the future together but he always says "maybe one day or we will see". I questioned him about this a couple of months ago and his response was "I am not sure what I want, who knows what the future holds". Well that didn't make me feell to good! I have invested 10 years into this relationship and I love him dearly but he will not commit to any future....Do or leave him and be free to look for a life partner or do I stay and hope?