It all depends on how often you go out, how fast you progress, how eager to learn you are, and who you wing with.
I'll tell people that they can learn more from 4 hours of in field work than they can of 4 days of reading.
Logically, the more you go out, the more experience you get and therefore, the more you improve. Going out only once a week is not nearly as good as going out 5 times a week, understand?
Also, depending on the person, if you have a knack for PU then you may progress faster than someone who is way worse off than AFC. You get what you put into it.
One final point, haveing a wing who knows what he (or she) is doing is very helpful. He can help you identify your sticking points, point out what you did wrong in set, give you in set advice (which is quite tricky), and help get rid of obsticles for you. A good wing is KEY.
To help you find a wing, I would suggest to check the local lair or check out PAIR:
http://www.fastseduction.com/pair.shtml
both are great places to find someone who is about your level, and in the local area.
~Kurent