Does using the fastest shutter speed reduce a camera’s lifespan?

Generally, no. Using a camera’s fastest shutter speed does not meaningfully shorten its life compared with using slower shutter speeds.

On cameras with a mechanical shutter, the shutter mechanism moves through its normal cycle each time you take a photo. At slower speeds, it opens and stays open longer; at faster speeds, the second curtain starts closing sooner. The parts are not necessarily moving faster just because the selected shutter speed is faster.

So shutter wear is driven much more by the number of actuations than by whether you shot at 1/60 or the camera’s maximum speed. Mechanical shutters are designed to operate across the camera’s full shutter-speed range.

For many point-and-shoot cameras, there may be little or no traditional mechanical shutter wear to worry about. Mirrorless and DSLRs can still have mechanical shutters unless you use a fully electronic shutter mode.

Bottom line: always shooting at the fastest shutter speed is not considered a significant factor in reducing camera lifespan; total use of the shutter matters more.