Our planet Earth is so much more able to defend herself and re start on a new path I just laugh when Scientists try to claim that we can somehow alter the Planets destiny. Maybe we can alter our own destiny on this Planet but even then it would not be too long before all memory of our civilization were erased until some future generation of Archeologists dug up our ruins. The blip that is this modern growth spurt is one heartbeat on the grand scale of everything this planet has seen or will see in the next billion years.
How many times can it start again?
As many times as it wants to.