My mother was diagnosed with advanced dementia and she has bad days and good ones. How much longer can I expect to be taking care of her in her condition?

This morning one of the bad mornings. When I went to her room, she looked so very sweet and also talked that way. Then she had to go to bathroom and she was in much pain so had to go thru a little to get her to take pain meds. Not too bad today as some days go extremely bad as she hates the meds and keeps asking same question over and over about what to do with pill and have to explain how to swallow. Then this morning had to assist her to the bathroom where she stayed on the toilet for long time and then needed to assist her off toilet and had to clean her. She then went back to bed with assistance and slept until caregiver got here to give a shower a provide 3 hrs time leaving less than 2 hrs by the time finally got out of house to go quickly to do grocery shopping, etc. that could be fit in. She really is so sweet at times but her hands ache and other body at times and she needs 24/7 assisted care. I really have no time to myself except for little I get each week, which is definitely not enough!! I love her dearly but this is really no kind of life for her or for me for that matter! But try to do the best we can, me and my brother and he can't do any of the private bathroom things as he doesn't feel comfortable so I am basically stuck here the majority of the time. It really bothers me so much to see the suffering she goes through with the pain she experiences. I suffer much when she does! Tried to get bridge to hospice but VNA said she did not qualify as she can still eat and walk. How much longer can I expect to be taking care of her in her condition? Guess no one really knows but it is the most depressing thing to be going through, with her suffering and mine. Love her dearly so try to do my best.