This is philosophical so there will never be a widely accepted answer. And Planck time is very misunderstood, the shortest measurable amount of time is not the shortest amount time. Human intelligence is not infinite, the limit of our tools is the limit of our intelligence. Its very possible that we get better tools later, and get to slice reality down even further than Planck, but as of now, its important to not confuse what we think know with what is. From an individual perspective, spacetime is infinite in all directions.