Do you keep it in the Fridge Eve?
If you do and only warm up what you actually use for each Rabbit then as long as a sterile needle is used to drawn up EVERY treatment it should keep for a couple of weeks. It has no antimicrobial added so I would not keep it any longer.
Bit of a Bummer as you dont often use an entire 500ml bag at a time...... :?
Janex