Have you tried practicing a couple of pieces each lesson? Maybe that should be your approach going forward. I don't spend any more than 20-30 minutes actually learning something new on a piece I am learning, and I then come back to it, sometimes the same day, sometimes a couple days later, I don't actually find forcing myself to spend more time learning something actually makes me learn more, or any better than just spending a short burst of energy learning, and the rest of the time thinking and revising what I learnt in my head, sometimes consciously, sometimes not.
Here's a question, do you actually like the piece? I like his Nocturnes and Nocturnes in general, and as a particular fan of Chopin, it's easy to see where Chopin's Nocturnes came from, so I have an appreciation of Field, even though some of his Nocturnes are a little undeveloped.
Maybe you are putting too much pressure on yourself to perfect it, too much of anything is bad for you. 2 months at an hour a day seems like a lot to be spending one piece, if it's inline with your skill.