There is a book called Orlando for Brits which comes out every year which I would recommend if you seriously want to go there. It goes into some detail on the tactics to use when visiting each park and which is the quietest day for each. It even tells you which entrance queue to get in and which rides to do first to avoid queuing as well as the fast pass system. Used to work like clockwork for us though my missus treated park planning with military precision!
We never did more than 6 days in Orlando before spending one night in Tampa to do Busch gardens then 2 weeks in either Naples, Sanibel Island, Captiva or North Captiva island down on the Gulf coast. Any more than a week in Orlando would drive me round the bend, though I used to enjoy some of the decent restaurants of an evening.
Sea world wasn't all that anyhow but the rollercoasters are somewhat better than owt on offer in the UK.