Sorry DURR, there's no such thing as "cheating" in modelling, unless you're talking about submitting work that's not yours in contests.
If you're just building for yourself, for fun and pleasure, then anything goes!
I never paint or detail something that will never be seen. I prefer to spend what modelling time I can find detailing, painting, and weathering only what can be seen. Even if it can only barely be seen, however, I'll give it the full treatment. Something that cannot be seen at all? Nope. I won't even use the parts, actually.
That's not cheating, or being lazy, that's just smart modelling, as Robert mentioned!