Many engine mfrs do this routinely, and no those engines don't get sold, as they are torn down afterwards for analysis.
Keep in mind they are connected to a dyno at the time, they aren't just freewheeling on their own.
I work for a research company that runs diesel engines at peak HP & torque non stop, other than normal oil changes etc. for months at a time!(or until failure)(750 HP-1500Ft/lbs)
Amazing sometimes how good a condition they are in, and how long they last!
Of course occasionally we get spectacular failures which are entertaining to say the least!
