Depends. If you want the reader to read all of it, then too long can be a problem (I freely admit to not fully reading profiles that take up half a page or more - unless I later find myself enjoying their hubs and then I'll go back to it). I also agree with Relache's point about wanting readers to easily see your featured hubs.
On the other hand, there is nothing 'wrong' with having a longer profile so that those who want to read more can do it (like Simeonvisser mentioned). BUT, if you do that, I would recommend putting the most important stuff at the start of the profile so that people like me who prefer shorter profiles can still get a sense of who you are before they stop reading.
Overall, my philosophy is to write whatever length of profile you'd be comfortable reading of someone else's.