Tests like the one which sinks in water is original and the one that floats is a duplicate one are not right. Even the ones made of wood with some lead impregnated in it can sink comfortably in water. The best way is to procure from reliable source.
Many get confused with the shape and size. One should not seriously worry about it. Just see that the Mukhi is well defined, corns and contours are natural, there are no cracks near the central hole and the bead has a good health. Smaller size is also considered to be very auspicious.
Rudraksha can be worn at all times. Some books say that Rudraksha could be taken off during sex, menstrual cycles, during visit to funeral grounds and during Bowel movements. Also it is advisable to take off beads while taking bath as excess soap dehydrates the beads of the natural Oil. They need to be worn with faith, respect and love.
Life of Rudraksh could be any number of years. If well protected, can be passed on from generation to generation.
Identification of real Rudraksha:
1. If you place a real Rudraksha bead in a full glass of water, it would drown in water.
2. Boil the Rudraksha in water for continuous 6 hours, if it is real rudraksha there would not be any effect on the rudraksha bead, else if it is artificial or two rudrakshas are joined together artificially (in case of Gauri Shanker bead), they will get separated.
3. Rudraksha bead shall not be broken from any end.