My mother is in the dying process, but I cannot get a read on how long this is going to take.

I know part of this has been asked and answered, but I feel like mom is on a different plane all together. She is 91 and suffers from severe dementia. She has not physically moved herself in anyway for over 6 years. She has been transported by a hoya lift during that time. She has been incontinent for that amount of time as well. She is in her 5th assisted living facility. She has been on Hospice 2 previous times and roared back to life but now on her 3rd time with them, this is different. She has lost an average of 8 lbs a month for the past 7+ months and is down to 114. She is bedridden now. She has had skin ulcers and breakdowns for over a year and then they are multiplying aggressively. She has all but stopped eating and drinking although yesterday she was able to sip a lot of water through a straw indicating some thirst is left. Last evening the med tech and I were talking about her experience of watching and treating her patients die. She gave me some behaviors that most people display such as agitation, or staring straight up to the ceiling or voicing the pain of dying. All of which happened last night. My mother who has not been able to move for years was able to pull herself up off the pillow, trying to sit up or reaching for something in front of her, but quickly fell back to the pillow. This happened about 4 or 5 times. I have not seen her move like that for years. She said ouch and ow, while just lying there, voicing pain that was not obvious to us, but she felt somewhere in her body. She does not talk anymore so this was new. But the more prevelant signs of dying are not there yet. Such as the apnea breathing, or the skin molting. Her hands are still warm. She does not have a temperature. She is not in a coma. She is sleeping a lot more, but she still has her eyes open at times and she responds sometimes when you call her name with her eyes moving towards the voice. She looks so frail and helpless and it is hard to watch. Every care giver at the facility is saying she is so strong and they have not really considered that mom is really dying. Hospice does though. I guess I just want to know how much longer can this go on? As with many of you, that are the single family member who is left or willing to oversee the care of their loved one, you understand this. I am a single man, never married with a brother and sister who do nothing. So talking to them is about as productive as watching paint dry. It seems many families are similar. Anyway, it is so tough and I have been with her for over 8 years taking care of all of her health needs, paid her bills, managed her money, insurance, prescriptions, doctor's appts and on and on and on. Believe it or not, that was the easy part. This is hard and I want this to be over. But I really just don't want her in pain anymore.