If its only a cople of months your fine...........I dont really no about codiene compounds i suppose it depends what else is in it.

But i know that codeine sulphate usually lasts for up to twenty years without losing its potency(if stored correctly of course) Theres numerous anecdotes out there bout folk finding like Morphine and codiene based medicines in there loft that were like 50 years old and they worked fine......

But check the expirey date in my expereiince it will prob be okay for a couple of months outside that

Peace