Not deuterium/tritium fusion, but rather deuterium/protium fusion: D + p --> 3He + photon. There is no tritium. The star is not hot enough for the 3He to then

Not deuterium/tritium fusion, but rather deuterium/protium fusion: D + p --> 3He + photon. There is no tritium. The star is not hot enough for the 3He to then fuse with itself, as it does in our Sun or to some extent in red dwarf stars. In the center of our Sun, the Dp reaction goes so fast that a D nucleus would be consumed in about 1 second. A lot of sources just say "deuterium burning", and people assume this is DD. But at low temperature, the reaction rate is strongly affected by barrier penetration, and this is strongly influenced by the reduced mass of the two nucleus system. The 3He3He reaction is slow in red dwarfs, and I understand the concentration of 3He in them builds up to about 1% before plateauing. I don't think any red dwarf is yet old enough to reach that stage. Red dwarfs are fully convective; unlike our Sun their entire mass circulates through the core and becomes available to undergo nuclear fusion. This (and their low luminonsity) makes them very long lived, up to a trillion years, far longer than the universe has yet existed.