This thread makes for such upsetting reading. I am actually appalled at the amount of women - always women! - who are taking on the care of elderly and sick relatives. It's never men putting stress on themselves and running themselves ragged it it? I think you are all amazing women, and very brave to come on here and admit it's like death by a thousand cuts looking after very elderly, infirm, and ill parents, and it will be a relief when they're gone (or it WAS a relief if they have already gone.) Especially when they don't seem to appreciate the help, and just throw critisism and complaints at you!
This admission is probably very reassuring to many people (women) that they are not the only ones feeling like this. I am worried that all the women doing this (as well as looking after their own children, and sometimes whilst holding down a job) is going to make them ill! 
My parents were a bit older when they had me and my brother (early 40s,) and they died in their mid-late 70s when we were in our mid 30s. Dad died after suffering from cancer, but died quite fairly quickly - within 8-9 months of being diagnosed, and mum died 6 months after him, just found dead in her armchair, and diagnosed as 'heart failure.' She went downhill quickly when he died, and became weak and needy and couldn't do anything for herself.
I did look after them both for just under a year and a half - because mum struggled with dad. I had to do it. My brother - who is 3 years younger than me - was nowhere to be seen. He had moved 100 miles away 10 years earlier, and only turned up for the funerals. But yeah, I looked after them, and it was hard going (I had 2 small children, and a job too, and a home to run,) but it was for less than a year and a half.
I can't imagine going through this for some years... maybe 10+ ... Not knowing when it's going to come to an end must be horrible. The relentless grindstone of care for sick and elderly people - who are often rude and obnoxious and ungrateful - is relentless. My parents weren't too bad, (and were quite grateful for my help,) but my mum was very critical of pretty much everything I did!
What's the answer though? Sadly I don't know, and I don't think anyone else does, because there is no answer. I have seen many women burnt out by looking after elderly, infirm, ill relatives (usually their parents,) and as I say, it's always women. Men (sons) never step up. Well, I've never seen it happen! Even in my own extended family, it was always my aunties, female cousins, nieces etc, looking after the elderly and infirm (and even my own mother looked after her mother when I was a child. Her brother didn't do it. She looked after her for 5 or 6 years until she died in her late 70s.)
Some people say 'we need to take care of our elderly/have them living with us etc, as they do in other cultures/other countries.' (And like some of us used to do here pre 1980s I would say...) But it's a different world now, and the cost of living is higher in the UK than some other countries, and house prices are very high.
And as has been said, both people in any given couple need to work now. Also, people move away to other towns, counties, and even countries, (sometimes for work, sometimes just for a different life,) so the family network breaks down. And so lots of pressure is put on the women in the family - usually just one woman, often the eldest - to look after the parents/run around after them, as well as working, and looking after her own children (and sometimes grandchildren!)
Who'd be a woman eh?!