I stayed in Japan for five years and finally left because there seemed to be no long-term career prospects. I am a teacher here in the US, and thought I'd be going back regularly. As it turns out, my son has severe autism and making that plane trip has not been feasible. I would love to go back, maybe for a year to teach again.
Stay while you can!
Have fun! These opportunities may or may not be available again in the future.