We try to use up open vials up as quickly as possible and put an in use expiry date of 6 days on them , if not used up by end of 6 days we bin them as we focus on using up opened vials rather than opening up a second set of vials we don't usually have a problem we use Diamed cells Have used both ortho and Diamed cards / cells over the last 20 years and I know which one I prefer - Diamed