[*]Or, and here's the important part, about every 4 sessions or so.[/LIST]
I agree with you that this is the important part, and expectations can be examined in light of it.
52 divided by 4 = 13, indicating that WotC expected one to reach approximately 13th level over the course of 52 sessions (barring any statements located that dispute Monte Cook which are deserving of more weight than this....something I find unlikely unless they are later statements by Monte himself).
Gary expected one to reach approximately 10th level in the same period.
So we can see, based on this information, that the expected rate of advancement (by these parties) for 3e is greater than that for 1e, although not too greatly so. (3e characters have 1.3 the expected advancement of 1e characters.)
That is less disparity than I would have expected (I would have expected a 1.5 variance, or 15 levels in 3e to 10 levels in 1e). My mileage certainly varied in actual play experience with 1e, and I imagine that others have had their mileage vary with 3e as well.
RC
EDIT: BTW, this is at some variance with Q's work, I note, which demonstrates in the AD&D modules that the 1e character rate of advancement was slightly higher than that of the 3e rate of advancement.....IOW, opposite of what the linked statements show was expected. I do, therefore, contend that I was correct not to accept the conclusions as "proven" on that basis. YMMV.
RC