Opened: 2 months in the fridge. Be sure to refrigerate after opening, and never leave mayo out of the fridge for more than two hours.
I make sure to take mine out of the fridge every day and put it in the sun for an hour and 59 minutes.
Packaging question. Why does the big jar of mayo which is more than I will use in a couple of years cost $3, while the 12 oz bottle costs $2.90?
The answer to the question “Why does X cost Y?” is always exactly the same:
Because that’s what people will pay for it.