To quote another bike forums member, I think we are slicing the baloney a little too finely here. So much depends on how you ride, in what conditions, and how many miles you ride as to make the only meaningful answer to the original question as, "it depends". There are folks who ride their road bikes only in good whether, and only for a few months out of the year. Such a bike, if maintained even minimally should be fine not just for 10 years, but quite possibly 20 years. Other riders subject their road bikes to such hard use that they can expect to replace some drivetrain parts in a couple of years.

One more thing. Off the shelf bikes usually don't come equipped with a complete groupset. Rather, the bike companies mix and match, putting a Shimano Tiagra rear derailleur with a Sora Front derailleur, with some non Shimano parts, like FSA cranks, or Tektro brakes.