>>12859817And where it stops? If ot stops it means there is something stopping it, so why there should be something stopping it?
And to the OP. The answer is: any.
Those that think we are alone could be right. Those that think the contrary could be right. In the end, it does not matter since millions of years can pass and we will be hit by an asteroid before any reply is concluded.
And existing life means almost nothing. 99.99999% of animal species on Earth are not intelligent enough to create interestellar flights, so, there could exist lofe but we could never notice it.