ASA priority

Hi,
I'm trying to understand a use case for using priority (QoS) in an ASA.
AFAIK, LLQ is a congestion management (i.e. queueing) tool.
Having the ASAs Gig interfaces, and usually 1:1 (i.e. no fan in),
when/how is an interface going to be congested, so that configuring
priority makes sense ?

To top this, you may think that doing shaping may create a "virtual"
congestion, but ASAs can not mix priority and shapping AFAIK.

Looking for some help understanding this...
-Carlos

-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net