Shelf life questions for emergency vials

hey everyone, i want to get a few Emergency Vials, and i have some questions regarding shelf life.

which esters and oils last the longest sealed?

would 4 vials in total with my current vial, be too much?

can I use them all before they go bad?

is the expiration date on astrovials actually true?

mine says 2033 for Een Castor oil

Thanks in advance :)