Do chains on single-speed last longer than those on geared bikes? I have a Jamis Beatnik (love) and ride on the single-speed side of my hub.  I'm wondering - derailleurs seem to me like they might 'stress' the chain (even if only slightly) more than single-speed in the process of changing gears.  Are geared bikes' chains harder to maintain / shorter lived than single-speeds'? 

(Background: I noticed I hardly have to clean my chain on my single speed, and it always looks great and feels tight.)
Single speed last longer and cost less.  More metal and less (no) flex.

SS comes in 1/8 and 3/32. 
I would contend a SS 3/32 of the same basic construction is stronger than a 3/32 7 speed because it does not need to be built to flex and it is not flexed. 

I am not finding any pictures of 3/32 SS chains and the chain on my SS bike is 1/8.
So I guess it is not really a straight comparison.
But a SS will take a 1/8 and geared will not so it is a fair comparison.  

Also SS is built to take the abuse of a fixie.  In a fixie the chain has to take the braking force and gets hammered.  Note the question is SS not fixie.