Three seconds is good enough to start, it will get looser over time.
The ofna diff lock lube is meant to stay in the diff indefinitely, and you should add more lube in rebuilds rather than trying to take it Off, to get a tighter diff. The initial diff tightness will never last long, because of physics, and it will not get as loose as anti wear grease if no oil got in there. Oil got into mine and both Tires spin in the same direction with the motor if you try to spin only One tire: that's evidence of a tight diff(you can't do that with anti wear grease)...