We just spent 8 days at Royal Pacific. We did the two parks for 5 days since we had the 2days/3 days free tickets. We did everything several times and got there when it opened and left around 2, 3 o'clock when we were hot and tired (and it got crowded). My kids are 11, 8 and 4. Ideally, it would be nice to have 2 days in each park, US and IOA, but I agree with the other poster that you can do IOA in one day if you push through it and select and US in 1-2. You can do it in 1 day if you don't do a lot or any shows. When we do a trip with different parks, we try to put some down days in between for pool, relaxation, etc. but also for a "just in case" day that we like a park that we really want to go back to.