"Stored correctly and never putting a dirty needle in the stopper i think it can be kept till the expiration date. Again, never put a used needle into the bottle"
This is exactly how we handle them here... I'll keep and use at least up until the expiration date.
Store as indicated on the label... in refrigerator or at acceptable room temperatures, as stated on the label or package insert.
Killed/inactivated bacterins/toxoids can probably be kept and used for 4 months or so following 'entry', if not contaminated and stored refrigerated; modified live products... need to be used within an hour and a half or so of reconstitution.