on methadose 120mg/day for 6yearsl

I was also on MD at 130 mg's for 4 years.  The best way is to slowly taper off, as slowly as you can handle it.  Are you in a Clinic?  Can they work with you on this?  I had to be lowered pretty quickly because I was kicked off the program.  They lowered me 10 mg's every other day.  It was really hard.  While you are still at a high dose, it is not so bad.  If you do not have to leave the program, go at your OWN speed.  You can always raise and lower your dose.  Good luck!