personally I prefer only one liner. I don't find any tasks I'd encounter, even tough cutting tasks requiring 2 liners. I understand the use of the single liner as an anchor for clip screws, but not so much for strength.
My favorite incarnation of the Civilian is still the slender non-liner g-10 version, plenty strong enough.
I guess because of my training I'm real sensitive to weight differentiation. I can physically feel how much more drag is increased with the addition of one liner and especially two.
The only instance where dual liners are acceptable for me is if they are inset/nested like some Spydercos, or skeletonized like alot of benchmades linered models. These types maintain strength through rigidity without all that weight gain.
take care,
Ken