Just store it in a closet where it is cool. I do this for many years. I have blend last week 3yr old nitromethane and methanol for my neighbours buggy and it runs great. Just a small tip from me: if it is ready to run fuel just put 2 or 3 large (4mm or 5mm) stainless steel nuts in the jug and before use shake the jug entirely to mix the oils, nitro and methanol again.