In a 2 week holiday we probably spend 3 or 4 days at US/IOA but it depends what you enjoy doing, we love Curious George water area as we have discussed in another thread recently. Can easily do 3 visits of 3 or 4 hours each visit in a 2 week holiday, prefer it to a water park. We get a lot more value out of our US AP's than our Disney AP's
SW If you have a free day and have some spare money do a tour. It takes about 6 hours starts around 10 am get bottle of water go stroke penguin, front of line on rides, feed sea lions and Dolphins, reserved seating at shows(middle, perfect seats) and includes Lunch next to Shamu, all you can eat buffet.
It cost us about £30 each with AP'S so probably about £40 each without.
I think its a good way if you do this on first day then go back in on free day and everything else you don't see on the tour.
All depends how much of a budget you are on but we loved the tour, I think they limit the group to around 14-16 people.