Come on Tropo! We're talking about normal ops here - you get in a hole and firewall the thrust levers. Unless you do some switching first, what you get in the modern Boeings is rated thrust.
Now, on the classic B747 etc. it was possible to overboost. That was an advantage of the design to me - when the sh1t hits the fan you can get all she's got and maybe fly away. Sure, the engines might be shagged, but the airframe is still OK, not to mention the occupants. Nothing buggers up a nice engine like whacking it with a hill!!!