not really. For one millis() and Serial interrupts will still be firing.Secondly SerialEvent() is still being called by loop.
put it into an infinite loop that doesn't do anything
Thirdly why on earth would you do it that way?
Secondly SerialEvent() is still being called by loop.
Only if the function is defined, and only if there is serial data to process, and only if the end of loop() is actually reached. Calls to exit() make the last part the most unlikely event to actually happen..