Despite the old adage, sometimes it is good to beat a dead horse. You may have come to a few cursory conclusions and found some good-enough solutions, but that's not good enough. Early solutions often aren't the strongest--and they've probably been thought of before. Your job is to go deeper. Putzier calls it looking for the second right answer. "It takes a little bit of discipline because we tend to jump on the first, obvious solution to a problem."
Same thing is what often makes a punchline funny. The first right answer can be obvious to an audience. But the second (or 3rd or 200th) is often the one that takes 'em from A to C and sparks laughter.
Also, it's a good reason to stick with bits for longer periods of time. I've been doing that more lately and noticing it's often months down the road that the right punchline or tag will hit me. Of course, you've gotta have something funny enough in there at first to justify doing it over and over again.