Two years ago we did AK and BB on the same day in January. Crowds were LOW, so we were finishing up AK by early afternoon. It was high 60's, sunny, and felt great at AK, so we thought we'd spend the rest of the afternoon at BB. We went back to POR, changed, and got to BB within an hour. Just a warning--take it as a bad sign if you're the only ones on the bus to BB, and the lifeguards are wearing coats. We had heard the water is heated, so we rode the chair lift to the highest point and got on the family raft ride. We realized our mistake when we went under a waterfall of ice water. What a long ride that was! The kids got back in the water for a little while, and I had coffee on the beach. I guess just make sure it's really warm enough. It's definitely doable in one day.