I received a great question from a swimmer who uses this blog for her workouts. I thought some of you might be pondering the same dilemma so I've also provided my suggestion/answer:
I'm currently between Masters groups and am trying to tailor my workouts. Which workouts do you recommend if I can only get to the pool 2 - 3 times a week for 1 hour? I've been trying the A workouts but haven't completed the workout in 1 hour. Your thoughts?
Under the circumstances that you described, I suggest that you swim the B workout, but adjust the intervals to be challengeing for you. This way, you are able to come closer to completing the entire workout (instead of missing the last set and cool down). Maybe use the B-group sets but insert the A-group's intervals.