We're talking about the current state of the real market here, not abstract hypotheticals. Laptops overheating at 30% CPU usage is not a widespread issue in the real world; to a first approximation, the only way to get an ultrabook's CPU to thermally throttle is to keep at least one of its cores completely busy so that the processor stays in its boost state long enough to pump out serious thermal energy. Bursty workloads give the CPU too many opportunities to cool off.