> I have heard people say that excess capped honey should not be left in
> the hive because it temps the bees not to go foraging.  Is this true?
 
Usualy, if there are still empty frames (regardless of how many full
frames there are) bess will continue to forage as long as there is
nectar available.
 
> I once accidently left a full comb of capped honey in the shed, and by
> morning the honey was oozing out of its cells. I thought the cells were
> air-tight.
 
I take it the shed was cool???  Funny thing about wax, it melts when
it gets warm, and I would assume that if you have taken the frame out
of a hive, it would have been during summer, and I would suspect that
a shed isn't the coolest place available. :->
Hope this is helpful to someone.
Adrian.