I dealt with my gf's boys moving on from toys... we still share a lego minifigure passion even though they're 18 and 15 though, but I dealt with the Star Wars loss... It sucked. Now I'm dealing with one going to college and the other one fixated on sports and video games. Things we share, but the toy thing sucked when it faded.
They've become my friends and I'll be seeing less of them as the years go on. It was something I totally didn't prepare for.