Before the advent of the offset account, paying more frequently than the standard monthly payment would save a significant amount of interest over the term of the loan.
If you choose a basic variable rate loan, without an offset facility it is still wise to pay weekly, but those loans are gradually being phased out, in favour of the offset package deal. There was a time when the basic loan was a substantially cheaper mortgage, but lenders realised they could obtain a larger share of the borrower’s banking products by packaging up an offset account, mortgage and a credit card so they are now offering these products at similar rates, making offset a much clearer choice.
Having funds in an offset account is the same as making daily repayments with all your day to day funds, the frequency of repayment makes no difference to the interest charged, and becomes simply a convenience to match up with pay cycles.