<human>: Condense the text into a few key points

I have been watching through SG-1 for the first time (love it, takes me back to ST TOS and ST TNG).  I just finished Season Nine.  While the Ori are cool enemies and a creative step up from the Replicators and Goa'uld, I can't help but feel the show should have ended at Season Eight, more specifically after the episode "Threads."  Everything is just so well tied together at that point.  The Goa'uld have been defeated as have the Replicators.  Anubis is gone, the Jaffa are free and all is right with the world.

It finally seems as though nothing now stands between O'Neill and Carter and Earth is safe after a decade of conflict.  NB I'm not even that upset that Richard Dean Anderson left the show.  Ben Browder does a great job but I feel from a plot perspective the show was all tied up after Threads.  The scene of the whole team at O'Neill's cabin would have been such a cool way to end the series too.

Am I alone in wishing SG-1 had ended after Season Eight?  Season Nine was good but it just felt like trying to milk a good thing too much.

If you think I am wrong (and I very well might be) then what am I missing?  Why are seasons nine and ten important to the overall plot arc of the show?
<bot>: Give me any reasons why Seasons Nine and Ten of Stargate SG-1 are (or could be seen as) integral to the shows overall plot.