It's more than reciprocal. Fusion rate and luminosity go up enormously with stellar mass, like m^4 or even higher, so the lifetime goes more like 1/m^4. Siriu

It's more than reciprocal. Fusion rate and luminosity go up enormously with stellar mass, like m^4 or even higher, so the lifetime goes more like 1/m^4. Sirius for example is 2x the mass of the sun, but 25x as luminous, therefore 2/25 the lifetime until it runs out of hydrogen.