I asked a production manager in Bakersfield about why pumps don't work 24/7. He said that the pumps shut off for a day or two to allow "pooling" of oil. You might think of this as ice melting in a glass. . .if you leave it melt a bit, there is more water to drink. . .maybe not a great analogy, but you get the picture. . .that is what the BP guy said, that more pressure when they resume.