As others have said, it varies with the person, the instructor, schedule, etc.

I had a student who was an experienced full scale pilot who spent some time on an RC simulator. He soloed after just a couple of trips to the field, and could have been sooner if there had been more time for him. His biggest "problem" was getting positioning right when doing a landing approach. After he had that down, he was on his own.

There is another student in my club who has been a student for a couple of years now.

And there are lots of folks in between. I've had students who I felt I had to "push" a little to get them to not stagnate on the buddy box and keep moving towards being solo. Guys who never would have started doing landing approaches until I basically told them it was time. And I've had students I had to tell, "yes, I know you want to do landing approaches, but you really aren't quite ready, let me see you do X,Y, and Z first, then we will landing approaches". And so it goes.