Spook, if crowds are reasonable and all you want to see at Universal is the Harry Potter areas, you could easily do it in just one day. If you want to see the rest of the two parks, then two days is plenty. On my third day, the only thing I did that I hadn't done before was walk through the Dragon Challenge ride queue, which isn't all that interesting, just a bunch of banners and a flying car.Alicemouse, go on and do it! As I said above, you can get it all done in just two days, and the Potter areas are well worth seeing. Next time you have an AP and have several trips planned, do it.
Thanks!
We usually blast through both parks in a day. I think I'd like to have 2 days at HP to make sure I see everything