FASA Games, Inc.

I see.

only the question remains now, that if two absorb charms are active and "turned on", will they effect add up and absorb the first 24?

Sure. Remember, though, that the protection they provide can be bypassed by an armor defeating hit.

Besides technical stuff: these things are expensive.
An Absorb Blow charm might represent around 3 months salary for a regular working type. Or alternatively, living in a slightly below-average tavern for a month (getting a room there, eating every meal there).
Your average person couldn't afford it. Those who can might also be able to afford adepts for protection, or are a threat because of their wealth, or are the leaders of groups (e.g. bandit lords).