Planning sufficent operating cash

For you conveyor wash owners and operators -

I have heard some conveyor car wash owners say that they try to keep cash in the bank that equals 3 months of expenses and loan payments. Some try to keep 6 months.

How do YOU determine how much cash for operations (not for equipment replacements) to keep in the business accounts to absorb temporary to intermediate dips in cash flow? What other sensible methods do you know of?

Thank you.

Alan Bussey