It's not just The Boob Guy.
I've had moments where an old favorite model just doesn't seem very big anymore or, alternately, as though they're suddenly not big enough. I've had the same thing happen while browsing collections where the woman looks bigger in one type of pose or angle; I start losing interest after awhile until *bam!* I find a pic of her leaning a certain way. Fish-eye lenses and/or perspective could be partly to blame.
Mostly I figure it's just humanity's overpowered ability to adapt to any situation: given enough time, people can get used to just about anything until the once-extraordinary becomes mundane. I hear there was a time when shooting several tons of steel into space at many times the speed of sound was amazing, but nobody really cares anymore when another rocket is launched out of Florida; the novelty has worn off as it's become commonplace. I don't see why the same can't apply to massive breasts.
Boob Guy, I recommend just taking a break for a little while. Unless, of course, it's the novelty of finding a girl who's bigger than all the others, in which case... um, start learning how to draw/morph really well? I don't know. Good luck, though.
2D vs 3D. See women HALF the size of whom you mentioned IRL and you'll be floored.
I can look at BE Shine all day long (quite happily) but there is a woman I know locally who has 3000cc implants (1/3 BE Shine's size) and I avoid her like the plague. (As in, they look SO BIG that they scare me, but I like it).
I can definitely agree with this, too. Makes me wish my area wasn't lacking in the big-bust department. We definitely ain't got whatever's in Poland's water around here.