It is all about the bit load per rev. Each flute of the bit can cut a certain amount and not overload. The faster you can turn the spindle allows you to feed faster and still have the same cut amount for each flute.
Now a s long as you have the power to turn the spindle at extrem RPM AND the power to feed at extreme high feedrates then the load on the bit flute is always the same as long as the same ratio to RPM and feed remain the same.
this holds true up to the point that you can no longer supply the proper coolant to keep everything going. FOr extrem high feedrates a high pressure volume coolant sytem is required.
BUT let that coolant get overworked and have 1 flute LOADUP and the bit will be history as well as the part. The failure happens at extreme speed as well (;-)
(;-) TP