Talking out my ass, but my feeling on tolerance is that tirz counteracts the signals my body is normally giving with regards to hunger, and those signals increase with every pound I lose. So it seems like if I did not change weight, the effect would stay the same -- i.e. not tolerance per se, at least not the way it works with many other drugs.
So based on my unscientific theory, Dwight's body is giving such strong "FEED ME" signals due to the amazing weight loss that it is difficult to get enough effect from tirz to adequately counteract it.
Personally, I am not quite at a plateau yet but I think I'm close. I've gone from 284 to 201, and I've been sitting around at 201-204 for the past couple weeks. The trend still looks like it is headed down, but veeeeery slowly. I've been doing 5mg twice a week, until this morning when I ratcheted it up a little to 5.5mg. I feel like my appetite suppression has been basically okay, and if I overeat just a little I still pay dearly with nausea (pulling off a Dwight-style 6000 Calorie day would probably put me in the hospital right now), just not really losing like I was. Still have 25 lbs to lose, for sure, so I'd like to keep chipping away at it.