my 1 cent worth
some good comments here.
I would try and not let a DNF worry you. with over 2 million caches out there, no one will find them all.
Every one plays this game with different goals (and skills) ....for us, a DNF is not a biggie....oh, we have plenty. For us personally, we enjoy going to the location as much as the find....but then, we are not urban cachers!
On the accuracy front....you should also remember, the coordinates will also depend on how precise the cache owner was when he/she took the mark....there can be variance there.
There is also some variance between model of GPS used, although that gap is closing.
Don't let stuff bug you...it is a past-time...to enjoy.
Cheers
Pete