O.k I've insulin before but its been a few years back so I need to get familiar with again b/4 I start using it. In the past I only cycled insulin for 4 weeks and threw the vial away. The vial has comes in 10ml, can I keep the vial and use the leftover insulin on the next slin cycle that I do or does insulin go bad after a certain amount of time even if it was refrigerated the whole time? I guess question is do I need to use a new 10ml vial every slin cycle?