Very interesting indeed! I just logged in with the very intention of finding out if anybody else has had this experience and found this thread.
I've been noticing with each consecutive use of 2C-B that my onset has been shorter while the trip effects (body high and visuals) have been increasingly intense.
My very first time with 2C-B I played it safe and took only 10 mg. The effects were very mild. I mainly just noticed some tingling sensations, increased light brightness and color vibrancy, and increased "giggles" (it seemed like just about anything and anyone around me was somehow so funny)...
On my next three trips I stuck to a 20 mg dose, which provided nice visuals, patterns, color vibrancy, illusions of objects moving, flowing, breathing, and morphing... as well as what I'd describe as a pleasant tingling/vibrating body high and increased Energy and sociability. After the first of these three trips, I'd thought that I'd found my "comfort zone"... On the second, my come up was twice as fast with slightly more intense effects and a similar duration. On the third, the come up seemed ridiculously fast, something like 5 minutes, and the effects went full-blown psychedelic within the first hour. After about an hour and a half of that I felt completely overwhelmed and recall having a sense of "letting go", because I felt that I could no longer control the trip. I would not call it a "bad trip", but it was much more overwhelming than I'd ever previously experienced with that dose. I got an odd feeling of my body being no longer mine, my skin going from tingling to completely numb, and an odd sense of confusion. Into about the fourth hour of the trip, I began to feel like I was returning to my "normal" trip state that I'd previously experienced on this same dose.
Since then, I've tripped only one more time, this time taking only 10 mg again, and was very surprised to experience a rich trip that was comparable to my first ever 20 mg trip. The only difference was slightly less intense visuals. I did not expect this 10 mg trip to feel so much stronger than my first 10 mg experience (it felt about 3-4 times stronger) and so I began to wonder if anyone else has gotten this sort of "reverse tolerance" experience with 2C-B! Glad to see I'm not going crazy. ?
P.S. Each trip was about 2-4 weeks apart.