I transitioned for 12 months before cutting off a great deal of my relaxed ends. (I trimmed the last of the ends off 6 months after the initial cut.) I blended the two textures by roller-setting my hair 1-2 times per week and wrapping my hair nightly and securing with a silk scarf. I think this method helped me to retain the health of my hair without having to apply too much heat. I didn't experience any breakage.
You have a lot of options for a long transition. Good luck!
Last Relaxer: July 2006