When is the sirius B star going to burn out?

Sirius B, also known as the Pup, is actually a white dwarf star. It has already finished its main sequence phase and is no longer burning hydrogen as a main source of energy. Instead, it is supported by electron degeneracy pressure. The time scale for a white dwarf to cool down and burn out is extremely long, much longer than the age of the universe. So it is unlikely that Sirius B will burn out anytime soon.