Does methadone loose its potency if its not stored in a fridge,and if it does how long before?

I have never heard of putting methadone in a refrig. I've been taking it for a little over 3 years now and i've never put in in a refrig. The nurse at the clinic I go to said it makes absolutly no difference. Maybe this might help.

on the bottles of methadone mixture my flatmate gets,(which is 1mg per ml to avoid confusion it says the drug will need to be consumed within 4 weeks after opening.This is put on there by the manufacturers not the chemist,so unless the bottles are full they have aready been opened,unfortunately it does not mention a fridge.