With Star Wars, that's not a problem, 'cause the characters are naturally jumping from place to place as it is. The scenario generally starts with the PCs coming out of hyperspace, and ends with them jumping back into hyperspace, nice and neat. Plus, the PCs have a patron -- i.e., the Alliance, who tells them "go forth and do X," and they do it. In D&D, the characters are more autonomous. I've started to set them up with a patron out of convenience, but it's purely on an "at will" basis on both sides.
When 3.5 came out, I decided to start a new campaign, but the character group just didn't gel properly, so I gave up on it and "rebooted" my previous campaign. However, it's been kinda sputtering the whole time because of my whole flakiness problem. I'm tempted again to try a new campaign, one with either a strong "You work for X" background, or a purely episodic setup (today, you are in Geoff ... next adventure, some unspecified time later, you're in Blackmoor). But I'm afraid the players would revolt! Plus, jamesbarrett is talking about doing a secondary campaign of his own to bring in pholph as a player, which would be a lot of new games flying around.
For the time being at least, I'll try to keep the current game going through to something that would make a satisfactory "the end." Then I can put some thought into how to make the next game better right from the start.