public Duration getStableTotalDuration() {
        return terminalStateInstant.map(instant -> Duration.between(callAcquireInstant, instant)).orElse(Duration.ZERO);
    }
Get time from just before trying to acquire lock to the time the terminal state was reached, or ZERO.
zkfacade/src/main/java/com/yahoo/vespa/curator/stats/LockAttempt.java