default @NonNull B expiry(long duration, @NonNull TimeUnit unit) {
        if (duration <= 0) {
            throw new IllegalArgumentException("duration must be positive");
        }
        long seconds = Objects.requireNonNull(unit, "unit").toSeconds(duration);
        return expiry(Duration.ofSeconds(seconds));
    }
Sets the time when the node should expire.

<p>The expiry time is calculated relative to the current
system time.</p>

@param duration how long the node should be added for
@param unit     the unit <code>duration</code> is measured in
@return the builder
api/src/main/java/net/luckperms/api/node/NodeBuilder.java