Knowing that all good things must come to an end doesn’t make those endings any easier. If you’re a fan of the Tokyo String Quartet, it wasn’t welcome news that the ensemble is breaking up after four decades of international performances. Feel better by giving the group a big send-off when they play at the Performing Arts Center on January 27 as part of their farewell tour. The program includes works by Beethoven, Mozart, and Mendelssohn.