Whenever you feel like it! As long as you have valid securities for the company's loan. You only pay interest rate on the amount you have borrowed at every point in time.
The maximum length of your loan will be based on what securities that are covering the loan. But in general, a loan can run for as long as your company need it, provided that new invoices are added as security for the loan.
With Quick loan you borrow against your company's accounts receivables (all existing and future invoices). When one invoice becomes due it ceases to be a valid security, but as long as new valid invoices is created in your invoicing system, these will be automatically added as security for the loan. With this, a loan can run as long as needed.
If you borrow against a specific invoice, the loan will become due at the same time as the invoice. In order to retain your loan, you simply have to renew the security by adding a new valid invoice as security. This is all extremely simple and hassle free.