It's a parallel to modern "3 strikes and you're out".

 

First offense, be bound against committing your crime. This is sufficient for the age reduction! (from Semirhage's POV).

 

Second offense, be bound.

 

Third offense, be bound and *marked as a criminal*. This is comparable to branding thieves, etc.

 

This is why Leane and Siuan regained their youth when unbound- the Age of Legends, being egalitarian, would have wanted to guarantee that punishments were reversible. They became the age they would have been without the binding.

The Sammael quote was how the issue was raised, someone later questioned RJ, and he confirmed it. It takes more then one oath to cause the ageless look.