RE: NBSG ending -- it wasn't the ending I was expecting, but it was an appropriate ending for the series. Left you with an uncomfortable feeling, which is pretty much what the whole show did.
I think Ron D. Moore felt it would be better NOT to stretch the series out longer -- there was an ending in sight - they find earth. You can't keep searching -- the universe is only so big....
(And the audience can loose interest if the same old thing is shown season after season...)
My $0.42,
-Z-man.