Why is it written that its shelf life is one year, but should be used within 45 days after opening?

Why is it written that its shelf life is one year, but should be used within 45 days after opening?

Our Pure Rose Water is 100% preservative-free and natural. So, if its bottle is not closed or sealed properly after opening, there is a higher chance that it will quickly catch contaminants from the air or other contaminants. That is why it is recommended to use it within 45 days after opening and close the lead tightly or seal properly after every use.