The point about sanding and pitchbleed is an important one; the pitch will run when the sander hits the wood (from the heat of the friction) if it has not been set properly. It has nothing to do with the pitch running after the floor is sealed.
Our home had 1x8" T+G white pine flooring installed when it was new, and sure enough after the first winter there were large gaps between just about all the boards. There is also some significant cupping. It's a little better in the summer, but it was obvious that it was not properly dried to begin with. Gives the floor some "character" I suppose, but a little disappointing.
Two years ago we replaced half of it. Found a few boards that had the mill's name stamped on them. As a kiln salesman, I remind this mill every now and then about my floor just for fun.
The bottom line: make sure it is dried properly, or it will bug you forever.
