I'm actually going to differ slightly in opinion from the others. I have had exactly the same experience as you had from cutting back on the medication doseage. The only difference is that I did it in conjunction with my PM. He actually requires that all of his patients take a "drug holiday" once a year for 1-2 weeks in order to mitigate tolerance. As a result, I haven't had to increase my pain meds for the past 6 years. My PM says that other than his cancer patients, the vast majority of his patients don't have to keep increasing their meds once a therapeutic dose is reached. From what I've heard from his other patients, they feel the same as I do. That week or two is pretty unpleasant, but being able to keep at a stable dose over the long run is well worth it.
I hope you will talk to your PM about this since it is important that your doctors know how much medication you are actually taken at any given time. I've yet to know a doctor who didn't support their patients desire to temporarily cut back on their narcotic pain meds. But it is your doctor's responsibility to keep you safe & he needs all the information you have in order to do that. On top of that, with the recent highly publicized cases of celebrities being prescribed wrong meds or too much of certain meds, the DEA wants even more careful records from doctors. Many doctors offices are just now moving to mandated UA testing. If your doctor knows about you decreasing your meds, it won't be a surprise if your UA test comes back with less medicine than originally prescribed. If you don't tell him until after the fact, it could raise questions about what happened to the rest of your medication. So I really am a strong advocate of being completely honest with doctors both to protect oneself & to protect the doctor's practice.
Glad you're feeling the benefit, just want to gently suggest that perhaps there might be a slightly better way to go about it. ;)