Legal Question in Wills and Trusts in New York

In theory, every NJ attorney is required to have a retainer agreement for each matter handled, even if they have represented the client previously. To me, an open retainer is one where there is not a fixed fee involved, and the fee is based upon an hourly rate; i.e., the matter has a retainer, and the final fee is based upon the number of hours spent on the matter. Since the number of hours to be billed is not known, the total fee is open.