You're probably partially aware of the issue, but it's not really a "ceiling" as much as a system of diminishing returns the higher you go. In simple terms, the Mu Opioid receptor is the one we're all after. Most Opioids that are commonly abused like Morphine or Fentanyl are primarily agonists of this Mu receptor. Buprenorphine acts primarily as a Mu receptor as well, but only in lower dosages. There is no tried and true dosage scheme to highlight what you're after, but I can tell you that the effects on the Mu receptor are most prominent at dosages below 2mg Buprenorphine.
In a perfect world, a person would be aware of these boundaries and never escalate their dosage beyond this. In practice though, people tend to chase the feeling produced by the lower dosages. In this process, they will still be hitting their Mu Opioid receptor, but as the dose increases Buprenorphine has a greater effect on the other Opioid receptors, which in short, is not what you want.
You are going to get the very best out of Buprenorphine by taking it in dosages of 0.5mg - 1mg. This positive ratio is going to start evaporating around 2mg, but will become very prominent around 8mg Buprenorphine. The reason people continue to increase their dosage is because they keep getting some of those positive hits to their Mu receptors, but the returns will diminish exponentially. I know very few people who get recreational effects from Buprenorphine using it in dosages regularly above 8mg Buprenorphine.
Basically, you are wasting your Buprenorphine. The only way to reclaim the feelings you're after would be to reduce your dosage. This isn't an effect unique to Buprenorphine, but the mechanism of the effect is pretty unique to Buprenorphine. There are other Opioids out there with multiple action like Buprenorphine, but they are not common in either licit or illicit circles. If you take enough of any Opioid, in my experience, you will become numb to the desired effects. Buprenorphine works a little bit differently, but the way of fixing the situation is the same in that you need to reduce your dosage.
The ideal dose is going to be under 2mg Buprenorphine, but as an Opioid tolerant individual, you might require 8mg Buprenorphine to actually make the medicine effective. At any rate, even reducing the dosage to 8mg Buprenorphine would still have a noticeable, positive effect upon you, considering what it is you're looking for.
