Good guesses, guys, but no.

Spokes generally break due to fatigue, or 'cyclic loading'. There are two components to fatigue - the amplitude of the stress as it goes from maximum to minimum and the average stress. If a wheel is not properly 'stress relieved' when built, then the spokes will lose a significant amount of tension after being ridden a few miles. If the spokes do not have enough tension, they go from completely unstressed when they are on the bottom of the rotation to 100% stress at the top of the rotation - a stress cycle with a huge amplitude - and this will result in broken spokes if the tension is not brought up. By raising the tension of the whole wheel (or keeping it high) the average stress is raised, but the amplitude of the stress cycles is much smaller - a spoke is never completely de-stressed, and it always has all the other spokes helping because no other spoke is de-stressed, so peak stress is also reduced.

For a heavier rider, a wheel needs to be either carefully and adequately de-stressed, or built with a higher tension initially so that when the spokes loosen from riding they still have adequate tension.