I was looking at the code, and it seems like you could put a low value for this and it would do what you want.

I did not try it though

  // sleepThreshold is the time at which if there has been no activity in the
  // tape file we insert a Sleep command
  const sleepThreshold = 500 * time.Millisecond

I tested it. It actually work, but their software crash, I had to patch line 153

  for lines[i] == lines[i+repeat] {
    repeat++
    if i+repeat == len(lines) {
      break
    }
  }

I actually went ahead and created a pull request to fix the bug.

https://github.com/charmbracelet/vhs/pull/446