I climbed Serendipity Arete on Mt. Owen in the Tetons a few years ago. It's a long, grade IV 5.9. On the way down, it started to rain and the descent didn't look as easy as it was supposed to be. After wandering around for a while, we rapped down two full ropelengths just as it got dark. Out of water and in a hurry we blasted past the descent gully twice without recognizing it. At some point we realized that it was going to be a long night, so we found some water, sat down and ate a little food. When we started again we walked right to the spot and down to the tent. The plan was to camp at the trailhead Friday night, hike in to Valhalla Canyon Saturday, then climb, hike out and drive home on Sunday. We didn't make it home Sunday night, we spent another night in Valhalla before hiking out early Monday morning. When I called my wife, she told me that they had already called the ranger station and were told to "give 'em another day, people get spanked on that route all the time."
The moral of the story is, if you have to ask yourself whether or not you should call rescue personnel, you probably should. They usually have a good gauge of what we fools are up to. To reiterate the above sentiment, I would also rather meet a lost person at the trailhead than head out a day late for a body recovery.