How does a star's vastly increased luminosity due to high mass affect its main-sequence lifetime?

The lifetime is drastically shorter because fuel is burned so much faster to counteract overwhelming gravity.

There is a critical cosmic trade-off dictated by mass: while higher mass grants immense immediate brightness, it comes at the cost of longevity. Because the more massive star is dealing with overwhelming gravitational forces, its core operates under much more vigorous conditions, compelling it to burn through its hydrogen fuel reserves at a terrifyingly rapid rate. For example, a star five times the Sun's mass might only last about 100 million years on the main sequence, compared to the Sun's expected 10 billion years. This accelerated consumption ensures a brief existence for the most luminous stars.