In my case, when I was first starting I scheduled 2-3 lessons per week and ended up getting 1-2. These beginning portions are where you're first getting the feel for the airplane and learning it.
By Thanksgiving of last year, I had probabably somewhere in the 20-25 hour range. I'd soloed and had been signed off for unlimited solos within 25 mile radius of IPT. Then, for 6 weeks I didn't touch an airplane, due to chaos in my life and bad weather. By early/mid January when I got in an airplane again, my instructor went around the pattern with me 3 times just to make sure I remembered how to fly before I went off on my own. Yep, by then I was a little rusty, but I was amazed at how little things had changed.
By comparison, I have a friend who's probably at close to 30 hours now, hasn't soloed yet, and probably won't for another few months. He plans 1 lesson a week, which is frequently cancelled, and then he's stopped and started his training a few times. By this point, he should have started thinking about solo cross countries, not just his first solo.