"Do not worry about tomorrow, for tomorrow will worry about itself. Each day has enough trouble of its own." Mt 6:34

If you are lucky - and one of the frustrations of my life is that all my former YFs have disappeared from my life due to circumstances beyond our control - he may well be around for a long time. Or he may get killed in an auto accident tomorrow.

By the sounds of it, you are very blessed in your YF; enjoy what you have, thank God for him, and be a true blessing to him. Maybe your relationship will continue for a long time, and in 30 years time, his son will be your YF as well...

But in the real long term - the one we will look at in eternity - what matters is our relationship with God, and that you and he rejoice together on that further shore. In that perspective, will being in his life have been good for him? Or for you? Maybe, maybe not. But that's the real test.