Ten years is a long time for any TV series to run, let alone a sci-fi series. And many TV series start showing signs of "too many trips to the well" long before the tenth season. Star Trek TNG and CSI (Las Vegas), to name two -- TNG lasted 7 years (and with a couple of exceptions, its seventh season stank to high heaven), and CSI it its current seventh season has become unwatcheable.
So I don't mind SG1 having a weak 10th season -- it's still a pretty darn good run.
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"Some mornings it's just not worth chewing through the leather straps." -- Emo Philips