Jeff O'Connor wrote:
I've always felt like DS9 ended precisely where it should have. There were more stories it could have told but they'd really been doing so well for several seasons at that point that it's difficult for me to imagine a non-war season successfully scrambling together a similar strength after the creators had gotten so good at the gloom.
Which is somewhat telling, DS9 knew it was getting 7 years. TNG was pulled after 7, so DS9 knew 7 would be it for them too. As a result they were able to pace themselves and bring the story to a natural ending point. Most other shows don't know when they're ending until almost the end.