The degree to which you need a refresher varies tremendously from one individual to another. I once had a class with 6 people, 4 of whom really didn't need it and 2 of whom should have taken the entire course over again.
I once had a refresher student who (with one glaring exception) clearly did not need the refresher from the very start. Once I saw her excellent performance in the water, I suggested it would be a better use of our time to work on more advanced skills, and she was quite happy with that decision. We worked on non-silting kicks the rest of the way.
I do want to talk about that one glaring exception, though. She had all her own equipment, and it was all pretty expensive stuff. When she put it all together, turned on her air, and looked at her air integrated computer to check the pressure, she said that the computer had analyzed the mix of the gas the shop had supplied and determined it was 32% nitrox. I told her that, no, her computer was still set for 32% from the last time she had set it, but the tank had only air in it. She insisted. I finally got through to her by explaining that the shop was not going to give her 32% for a pool refresher course; the shop did not have the ability to make nitrox in any percentage; I was the only employee of the shop that had the certification, knowledge, and equipment to make nitrox; and I did not put nitrox in her tank. At some point in the past, she had gotten 32% for a dive and had set her computer for it. She had assumed everything she had used after that was 32% because that is what her computer had said. It is possible that she had always requested 32% on her dives and so was reasonably close each time, but maybe not.
The point of that story is that this very good recreational diver had a glaring hole in her knowledge base as a result of her layoff, and it was a misunderstanding that really could have killed her. If she had dived a tank of air to the full limits of EANx 32, she may have gotten a very serious case of DCS.
