hCG is somewhat fragile. It is typically extracted from the urine of pregnant women and then freeze dried. It is usually all clumped together prior to being mixed with water.

hCG from the pharmacy or whereever is kind of like getting raw hormone in a way, I suppose, since you mix it yourself after receiving it.

All of the hCG I have ever heard of comes in an amp or a vial, but that doesn't mean that it hasn't been packaged differently by non-pharmas.

usually 1500iu and 5000iu in one amp. I mix up the 5000iu amp and preload slin pins to get 500iu per dose.

I've been getting the 5000iu amps and as you say pre loading them to 500iu, but as far as im aware they only having a 30 day life once mixed so im wasting quite a lot, being able to mix other amounts would be advantagous

get the 1500

They'd probably last longer than that in the freezer/refrigerator. Also, they don't just all of a sudden go bad. They simply lose potency after a given amount of time.
Sounds like your best bet is to get the smaller amps like Tommy said so you don't have to reconstitute so much at any one time.