well it isnt overclocking... the clocking circuit is in the pc..

The monitor has prefered setting because the electronics are designed to runn there.. run it outside these areas.. and chance of component failure increases dramaticaly.

An increase in the frame rate has an associated increase in the line frequency. the HV unit is built to allow a range of frequencies.. these are efficient and stable in these areas.. outside that.. the output voltages and random noise increase as well as the associated component heating.
Unlike a CPU or graphics card where your main enemy is heat.. here you have the spurious voltages to contend with.. and malformed waveforms....
Just beause the monitor can display it is not an indidication that all is well..more all is well on its way to destruction..