Tiny Cooling Fan of bearing selection

"Tiny Cooling Fan" bearing up choice, bearing mainly divided into two kinds of ball bearings and oil bearings, ball bearings and long service life, low noise, but the price is very expensive; "Tiny Cooling Fan" oil-bearing shorter life than ball bearings 1/3, after a period of time may be some noise (over one year), but the price is cheap. After more understanding since we can choose, but if some "Tiny Cooling Fan" prices and oil prices almost fan, it indicates which ball is old or out of goods do not buy.