I'm the same way, if I have time for it I actually prefer a couple of characters. That said, there are some RPs where that ends up coming back to bite me in the ass. It's happened more than once! BUuuut, MOST of the time I RP at least two characters, I've been known to go as high as 3. This is doubly true of 1x1s, where I very briefly had like 10 characters for a Harry Potter RP consisting of nearly entirely non-canons. Sadly, when the guild went down I lost contact with who I had that RP with and I cannot for the life of me remember her sn :( :(
But, back to the point, I definitely like to have more than one character!