I log my DNF sparingly
Alot of the caches around here require hours of hiking to get to the cache.
Or miles of bumpy roads to get close.
If I go that far I will spend hours searching to find it!
One time I put in the wrong coordinates and was off by 5 miles!
and logged it as a DNF, But made it clear in the log that I was stupid,
I finally gave up when all my AA batteries were dead (flashlight and gps)
Any ways I'll search long and hard before I log a DNF
then E-mail the cache owner begging for hints