Oh, wow - and I thought I´m obsessed!
PS: 3 - 4
CoS: 4
PoA: 4
GoF: 3 - 4
OotP: 2
And often I just grab a book to reread a special scene or chapter, depending on my mood. But as somebody already said, there are so many other books worth reading that I don´t reduce it on HP.
But I also like reading them all in order before a new film comes out.