moving from big bowl pipes to small...

When I started smoking (mearely 1 year ago), I read some veteran smoker's text about tobaccos and pipe shapes.
Besides the generic "flakes into narrow pipes", "virginias into thick walls" advises, I remember him stating that he always used smaller bowl pipes for smoking virginias, because by the end of the bowl the virginias would show all their splendor and he wanted to get there faster and more often, so even if he was in the mood for a long smoke, having two smaller bowls was better then having one big bowl...

I've followed those thumb rules, and virginias go in smaller pipes, while english blends (which are the ones I smoke the most) go into bigger bowls.

Also, I tend to choose the shape of the pipe according to some personal habits. For instance: I usually smoke virginias as the first pipe of the day, while taking breakfast or already at my working desk... so, a sitter comes very handy, because I'm multi-tasking and being able to put the pipe down anywhere is good.
One of my next buys will probably be a full-bent or 3/4 bent for english blends, which I smoke normally after dinner, while typing and surfing the web, and I need to keep my hands free.
These personal preferences are, in my opinion, the best way to choose which blend a pipe gets dedicated to. If, as an example, you like to smoke your churchwarden while reading, and if you read after dinner, then dedicate the churchwarden to the stuff you usually smoke after dinner.