How many neutron stars are binaries of other neutron stars? Hulse-Taylor binary, discovered in 1974, has orbital period of 7,75 hours. And the pulsar component rotates at 59 milliseconds. The orbit is also eccentric, from 1,1 to 4,8 solar radii. Expected to merge in 300 million years. PSR J0737-3039, discovered in 2003, has orbital period of 2,4 hours. The periods of the pulsars are 22 milliseconds and 2,7 seconds. Merger due in 85 million years. The one merger detected so far was noticed in gravity waves about 100 seconds ahead. What would be the present orbital period of a binary neutron star due to merge in, say, 20 years, so that we could design, fund and build observatories to get a good view? Does tidal friction operate on pulsars? About how long before merger, in which range of orbital periods, would tidal friction cause the rotational period of a pulsar to become equal to the orbital period of the neutron star binary?