I normally just have 1/2 hr lessons. I find them to be plenty of time to sort whatever issue has snuck into my swing.After my lesson today with James Robinson at St Anne's I would highly recommend him.
I have an over the top swing which I know I do but can't get rid of it. He solved it within minutes.
I only had a 30minute lesson, but I will be booking a few 1 hour lessons before the season starts and hopefully can get the handicap down again this year.
For me an hr can be overkill.