I think learning the whole PPL theory is a good idea, but you need to learn it, instead of just remembering specific subjects for an exam. As others said, this could kill you later in life, if not earlier. PPL theory will somehow help you with getting on with the ATPL exams, don't you think? I usually study a book for about 2 weeks and get pass marks over 95%, but I also work monday to friday and I'm at college after work for another four to six hours. I study when I feel good.. basically when I feel like it. I'm not rushing things. I used to have a schedule, and study everyday for 2 hours.. you know what? It didn't work, because after work and college, I got home some days at about 7pm and I was way too tired to do anything.. still studied.. and didn't learn anything. I need to concentrate on what I'm doing, I don't know how about you. I also have to study for my college work, as currently I'm doing Physics, maths and english at college. But I found a way to get my head around it. I do a chapter or two every night, then do the exercises on these chapters, next evening just have a look through it and study next chapter or two. It works. I study the stuff and I don't forget it. It used to take me ages to get through the books in high school! I could never get it into my head that easily, I guess another thing was that I absolutely hated some of the subjects at High school but that's a completely different story.
Just take your time, don't rush things. Learn it, don't just remember it.