It depends on how active you are on the site. I've seen some people go from level 1 to 10 in a matter of months (usually by answering a LOT of questions).
I've been on here a little over a year and I'm 14,461 as I write this. I was hooked for a few months and answered like crazy so I racked up xper pretty quick. I go for quality, not quantity in my answers though so it took me longer than it did for some others, although I did get a lot of best answers.
uhhh I have been on here for over a year now, but I wasn't really answering a lot of questions, it was more over time with in the last 8 months that I started to answer questions more often. The points I have just went up like my cholesterol and stress.
You can earn 5000 in like a month or a month and a half if your on constantly just give a lot of answers(good ones) get selected as best answer enter constes ask questions but it will only take a month or so to get it ...i have been on two months in all but I don't answer a lot of questions until I'm ready too but I have 3400 xper points and I answer about 15 questions a day until I go on an answering spree lol