Follow the manufacturer's recommendation for the spacing. In addition to expansion issues, if you snug all the boards up you won't have proper drainage and water will pool all over.
I try to avoid anything shorter than will span 3 joists. This may vary depending on whether the last bay is a full increment. It could be as short as 3'.Next question.
As I come to the end of the deck, I am faced with many options as far as length of boards. As the deck is some 40' long, I started with a layout pattern of
4'
12'
8'
16'
4'
12'
8'
16
I have an angle corner on the end that makes the deck boards all dif lengths and some will be very short. Is 48"' the shortest board length I should have, 32"?