I've been taking harmalas just about every night for the better half of a year and sensitivity seems to increase over time, like you said, while at the same time higher doses feel much more comfortable than before. Audio hallucinations seem to be more common than when i started this as well
I have experienced some variability in the depth of the experience even with the same dosage, but i don't think it has to do with tolerance. Many night in a row i've taken higher doses and no noticeable tolerance was felt, but it can be very different even with the same dosage-and sometimes even lower doses are deeper than a previous higher dose.. I'm not sure why some would experience tolerance while others don't
But I think for me a lot of it has to do with what i've eaten that day and my psychological state before/during the experience, and my ability to let go into the trance while maintaining awareness. Interestingly, probably the strongest 200mg of rue harmalas has been for me was the night before a drug test for this job.. I had been drinking a massive amount of water throughout the day and night and didn't think it would kick in nearly as strong as it did
<Ringworm>hehehe, it's all fun and games till someone loses an "I"