Bernhard (the most (in)famous member of these forums) wrote one should be able to learn at least 20 pieces per year.
Of course, the number of pieces one learns in one year is very personal. It depends on the length of the pieces, the difficulty of the pieces, current ability of memorisation and the way one practises. For instance, at my current level I could probably learn over a hundred of those eight bar pieces you find in beginner books, because they pose no technical challenges, they are probably in C major and they are very short. If you were to give me Chopin's Fourth Ballade, it might take me several months because of the technical challenges.
However, the 20 pieces per year is a good number to compare to. Because it will bring up several questions, the most important being "How can I make the learning and practising process more efficient?" If I were your piano teacher, I would not be happy with you taking such a long time to learn those pieces. It would be understandable if they were way out of your current level of technique and you had bad motor skills and you didn't practise, but you practise 7-10 hours a week. I would then ask "Are you actually practising during those 7-10 hours or is it just playing?" I would then get you to film yourself practising and spend a whole lesson on how to make it more efficient, pointing out places where you are going wrong so you can be aware of this and learn to be self-sufficient.
Having a mixture of really easy pieces and harder pieces is important. The easier ones you'll be able to learn faster, thus have a better sense of progression and more pieces to play. The harder ones boost your technique and are rewarding when you finally get there.