Formula

How strict r u when it comes to formula? I have 1 big can of formula that expires in March 2021. However I read that once the can is opened, best to use up all contents within 1 month. Any mummies out there use the same can of formula for more than 1 month? Reason is - initially I was on the low supply side and my confinement nanny suggested feeding FM in the night and I agreed because I needed the rest too. Now she is gone and I am feeding EBM in the day and latching in the night. My big can of formula is just sitting there..... I was thinking of using it for emergencies like I can’t be home on time and my other caregiver will be able to make FM for baby. But expiry date wise... pls advise!! I don’t want to waste it... still have 3/4 of the can.. if not I’ll rather bless it.. left with 20 days I think if I were to follow the 1 month rule.