It varies a lot with everyone. I think age can be a factor in some cases too. I know of an older guy who took almost 3 years to solo. Take me and my dad for instance, we both started flying at the same time with no prior experience, I was 15 and he was 52. We went out once a week and got 1, maybe 2 flights in a piece. I soloed by the end of the month, and he still hasn't soloed after a year. He's going to be waiting a bit too, because he just had a midair. I personally think my dad flew into the other guy, but they were both out of the pattern and at fault. Another thing that helped me solo so fast was the simulator. It's really IMO the first thing you should invest in. It's even helping me practice 3D and more advanced things now, so you can never really outgrow it. Not to mention it's more fun than most video games I own.