@Dante-Broggi's proposal of a ProcessClock also highlights an issue with Duration:
"15 seconds" on a ProcessClock is an indeterminate length of time, since we have no way of knowing how much physical time will elapse; the process could be suspended indefinitely, for all we know.
This also suggest that calling a Clock's duration "seconds" is problematic. For some clocks it might be "seconds", but perhaps "tick" might be a better term?