If you have reached a place where you can generally cope in healthy ways with whatever life throws at you without need of a therapist to help you through it, you are probably ready to go without. That was basically where I found myself about three years ago. I had worked through my PTSD issues (which probably caused me more problems than my bipolar episodes), and I found myself in a good, stable place, able to manage life and really not having more to work through in therapy. Have you considered just seeing your therapist as needed rather than regularly? That's kind of how my therapist and I left things (and I actually haven't been back to see him in like two years).