Level 7? Gosh, no time at all honestly. I got my PS3 in February of 2009. But ever since I got another Xbox 360 at Christmas in December of 09 I haven't played as much as I used too. So if I do the math I reached Level 7 around 3-4 months of casual play.
Level 9 (06/22/09)
Level 10 (07/17/09)
Level 11 (08/09/09)