what to do with the x-tra?

[steadygaining1]

Quick question, I am going to run 300 mg of deca a week w/test and drol. Question is I have 200mg amps, so I will be using 1 1/2 amps a week, can I just pre-load the remainder in the amp for use on the next shot. If so, I assume I should store it upright. Would I be better off wrapping the rest of the amp in tin foil to keep it fresh. Sorry if this is a stupid question.

[steadygaining1]

Thanks for the help!