When a loan is paid off are we required to terminate the UCC1 or can we "hold" it for future use?

Typically one month but you need to check your State's version of § 9-513. TERMINATION STATEMENT.

The national version and most state versions require termination within one month for UCC filings on "Consumer Goods."

However for other collateral (Inventory, Accounts, Equipment, etc.), they generally allow you to hold it until there is a request for termination, in which case you have 20 days after the request.