I think the realistic answer is that without spending tens of thousands of your preferred currency to set up a proper test environment and test a whole bunch of different cameras there's no real way to know.

Presumably the manufacturers test each model of camera to get an idea of how long they will last under continuous use (although I imagine that only the high end manufacturers test properly) and that figure, after suitable massaging, is the one they release to the public.

Edit for pedantry: If a camera will take, for example, 100,000 exposures before breaking then if they are continuous at, again for example, 5 frames per second then the camera will break after approx five or so hours. If the same camera is used to take one shot a day then the camera will break many years later.

Thus, technically, a camera used continuously will break 'faster', i.e. before, one used intermittently regardless of any other factors...