Double sided polygons are one of hose horrible artefacts which are tough to remove, like 3 point quads, the gits!
(and before you ask, yes you can!) 'Unify polygons' found in the detail tab is most useful for co-located polygons!
Band glue is your freind, when you have rows of quad loops, which are redundant, as is 'disolve edges' when you don't. As a personal recommend, don't have large ngons with holes in them, cut them in such a way they are 2 ngons, without a hole (use the connect tool - l). In my experience when you perform subsequent boolean operations and they break. Every now and again polygons get 'broken' and become inverted or go 'black' one simple solution is to triple them and merge them, which usually fixes them, massivelly pointed ngons are the worst for that, so I just do that as a matter of course these days. (shift t - shift z).
I agree with Al and others, you should clean 'unnecessary' polygons, but things like how many rounding polygons you are using are personal choice. GP - if you want I'm happy to share non-lossy optimisation techniques with you, just PM me or IM me