I cannot believe that only the three seconds of presence exist and the past is not existing anymore, the future is not yet existing. So, eternalism, the block universe is very convincing to me. This means, we are immortal in a certain way. Our life is like a video and the existence of a video will not end when it is not watched. So our life still exists when we don´t live it. In this case, free will is only an illusion and if we take the video of our life from the video shelf to watch it again, it will always be the same.
There is possibly an error in reasoning: The word existence has only a meaning if you are in time and eternalism stands beside time.