While I don't like getting a DNF, I don't really mind them either. I'd rather have one that I have to work for then one that it easy. I'll spend hours looking and when I don't find it, it just makes me more determined to go back out again and find it. I'll will though, usually wait until someone logs a find before I go back just to make sure that it's there.
Most of my most favorite finds have been ones that I had to go back to look for.
Recently I had a DNF due to the snow. I logged it but I'm going to wait to go back after the snow melts. I know I'm in the right area so I'm confident that I'll find it. I have a couple of more that I'm going out to look for, though I'm pretty sure I'll DNF due to the snow. To me it's just nice to get out of the house and into the woods even if I don't find anything.