Shape of pipe matters not a bit. A bent pipe will possibly pool at the bottom of the bowl and "gurgle," maybe even "steam" your tongue. The width of the bowl may cause a pipe to some with more flavor, while I wider bowl may smoke a bit slower. And yes, a longer stemmed pipe will smoke cooler as the smoke will go a later distance and possibly it might be cooled by the time it gets to your mouth.
As for how long a pipe will last, a cob should last a while, but a briar will last longer with less care.
Hope that helps!
Peace of the Lord be with you.