When do you know its time...

Question
When do you know it's time to put your dog down?  We have a golden
retriever that is 14 years old and cannot go up and down stairs anymore
but becomes anxious when restricted to the first floor.  She has fallen
down the stairs many times, has difficulty walking, and seems to be
becoming incontinent.  She limps (whether due to arthritis, old age, or
falling down the stairs several times) and seems confused from time to
time.  Her appetite is still good but we don't want to keep her if she's
in pain.  Also, what is an appropriate amount for a vet to charge for the
service?
Please do  

Answer
When the bad days out-number the good days and when her QUALTIY of life has declined, it is time.  It sounds like she is pretty uncomfortable and I am sure in some degree of pain.  You can ask your vet about arthritis medication such as Etogesic, Metacam or Rimadyl to see if that would help her as well as Anipryl, which is the new medication for dog Alzheimers, and Proin for urinary incontinence.

As far as charge for euthanasia, that is going to depend on where you live.  I would guess about $50; however, there may be an office visit or physical exam charge on top of that if you have not been to the vet recently.  And depending on burial or cremation, that will be an additional fee.