There should be a place around you that will store the semen, like a reproduction center or something. I know there is one in Missouri and there is one in Oklahoma. You can definitely store semen forever, there are straws available from bucks that were collected in the 80's, there is even some from before that.
I would personally buy 5 straws, you can usually get a slightly discounted price per straw when you buy it that way because each goblet holds 5 straws so they won't have to break it up. With a semen tank you have the tank, canisters (most have six), canes and goblets. The cane is a slender aluminum deal that is about 8 inches long or so and the goblets hook to this, you can hook 2 goblets to a cane so you can have up to 10 straws per cane. With buying 5 straws you will basically have 2 straws per doe and one extra in case one of them doesn't take.
The main thing you want to be cautious about when buying a used tank is if it has been allowed to go dry. Often when a tank goes dry it won't hold nitrogen any more, and with expensive semen you don't want to put it in there and find out your tank went dry overnight.
I would contact the Texas A&M they do a lot with reproduction and should know of a place near you that can store the semen for you. If you want to buy one, I bought mine for $550 from Superior Semen Works it is the Millenium XC 20 and holds up to 720 straws. It has 6 canisters.
