My mom finished radiation and chemo October 29. Since then she's had continuous problems -- mucositis, infections, swelling of the tongue to the point of not being able to talk, etc. She's been convinced that the cancer was back (or never was gone), but the doctors believed things looked good and she just needed time to heal from the treatments. She had a PET scan Tuesday, and today we learned that the cancer is "progressing" but is still contained in her mouth and neck area. They offered chemo again, but said that it would only give her more time. She said no. She's ready to die and to be finished with this terrible, painful ordeal. I would appreciate any advice and ideas on what we can do to make her last days less painful. Hospice has been contacted, and someone is coming tomorrow to explain their services. Also, the doctor hasn't given even an estimate about how long she has, just that it probably will not move that quickly. Can anyone tell me what determines how long someone in this condition lingers on?

I don't know the answer to your last question and probably your doc doesn't either--mine refuses to give me 'numbers' as he says they are so often wrong.
I can well understnad your mom not wanting any further treatment which will make her feel bad and give her less quality of life.
Hospice should sort out her pain meds etc. and everything needed to keep her comfortable.
From a personal point of view, I would say the best thing you can do to make remaining life the best for her is to ask her what she wants to do. And if it's in your power, arrange it.
I went to California to see my daughter in November--it shattered me, but was well worth it.
My partner and friend made sure the house looked nice for my son to come for New Year.
My chemo did give me more time, with relatively few side effects, but if your mom is in pain, then I think control of that is the most important thing.
And I would get out all the family photos, go through them with her and talk about happy times.
Just my thoughts,
Brenda

Far to many variables to answer your question with any degree of accuracy but pain management will become paramount. This disease does not end life without showing it's ugly side so be prepared for extremes. Their are a few posters who have witnessed it first hand who explain what likely to expect.

I have witnessed it with my mother and my best friend. Pain management was the one thing that really mattered to both. Not much else I can say except,, love her while you can and do whatever she wants. You have all my sympathy and prayers.