The only reason I think it's crazy is because at least from my perspective their isn't enough to do at the other parks to take up a week. Haven't been to Seaworld in years though so...
Don't get me wrong either I enjoy Universal, I got an annual pass while I was on the Disney College Program. It automatically renews at the same price every year, so even though I barely use it, 1 trip to the parks a year and it's pretty much me breaking even now between Ticket plus pakring. My day there usually goes like, walk into IoA, look at the Hulk line times, if it's not long just continue on with my day, if it is buy an express pass, go on Hulk, Spidey, P&B, Dudley (If open), Jurassic Park, Dueling Dragons (Haven't been there since HP opened), Look through shops in Dr. Seuss area, go to Studios hit RRnR, Mummy, ET (Which I heard might be gone next year), MiB, maybe Terminator, and I can usually get it all done by lunch. Then again when I go the people I'm with never want to spend the money on Universal so it's usually just me walking as briskly as possible from ride to ride. I also need to check out Transformers and Harry potter Land next time, I'm not a motion sim fan so I'll skip the HP ride and the Simpsons ride.
I also know people who never go to O-Town and decided to do Harry Potter and Seaworld for their Honeymoon, went to Disney just one day of their trip and regretted not making it the basis of their trip. So like I said, if you can visit the other places and have it take up all your time, I don't think it's crazy, but if your just about trying new stuff and riding what you like, like I am, there is not enough to fill up any decent length trip. I can tour both universal Parks in under 4 hours, which will change if the WWE HoF actually opens at NBA Zone, rumor right now, but for now I can, and from what I understand there is less to do at Seaworld and the like and I'm not a show watcher.
I feel the same way about Hollywood and AK as I do about the Universal parks as well, but transportation is easy enough where I can hit my favorites and get back to Epcot or MK with a reasonable amount of time.