Can only echo the importance of Power of Attorney in Health and Welfare. Finance too, of course.
If you don't have POA in Health and Welfare, the State becomes the decision maker for your parent's care, not you, should they temporarily or permanently lose mental capacity, be it a stroke or dementia.
a) When I say 'State' I mean your local Council, who can be pretty awful, the worst bunch of scumbags ever and wholly unaccountable, what's more. Everything you've heard bad about Social Services is true based on my experience. The whole foster parent racket always sounds like it's an urban myth but I wouldn't bet against it now.
b) You don't decide when they have lost mental capacity, someone else does. Don't get carried away with the 'shouting nutter pissing himself better off dead' narrative that's being put about. My mother knew who she was, who we were, where she was and we had a rapport with her, we could take her out for the day to a local cafe, but was deemed to have lost mental capacity. We paid full whack, Social Services owned her. Charming!
If you don't have POA in Health and Welfare, you won't even be entitled to see your parent's medical notes. You can see them after they're dead, mark you, but then it's kind of too late. If you see the words 'severe dementia' written all over the notes then you can expect some Liverpool Pathway-type stuff (killing thru a policy of dehydration) to be carried out by the care home and authorised by the Council, and there's not a single thing you can do about it. You are not the decision maker, they are. They can and will stop you moving your parent from a failing care home, and will be brazen about it... they really do hate the public.
As for palliative care, well, who the hell knows what this is? We got pressurised into this for our mother who had advanced Parkinson's even though she was on a fork-mashable diet and drinking a litre a day (when we advanced this argument, guess what? Social Services set up an unnecessary SALT test rigged for her to fail. She didn't.) It always seems to me that palliative care is a case of 'your parent has a few weeks or days to live, shut the door behind you'. We did not want our parent murdered by the State but of course, technically, it's not murder if they've lost mental capacity and you don't have LPA, just as it's not murder when Great Ormond Street turn off the life support with those kids in hospital. I understand it's different when someone has terminal cancer, but believe you me, the whole thing is stressful enough without the State poking its nose in and making it worse.
The other practical advice is to start to live every fortnight like it just might be your parent's last, and this is applicable to anyone who thinks their parent may not be here in a year's time. That way you don't put any enjoyable outings or events or purchases on the backburner - which is easy to fall into if you want to eke things out or have something to look forward to during stressful times. You are not really in control of this illness/process, though you can put out fires a bit, so watch out for exerting excessive control in other areas of your life just because you can, to subconsciously compensate. That includes delaying or stringing along stuff, sort of toying with it. Delayed gratification/ perfectionism has no place when dealing with the elderly. Also, when you get wind the end is near, you can't rush around doing all this stuff then, it feels heartbreaking and acting in bad faith, like you are selling your parent out. So get it all sorted asap, so you don't have to sort of segue into it when you would rather be in denial, things can just carry on a bit as before, do not have a list of things to do before your parent dies, it's implied that if you complete the list, it's all over.
Sorry to bang on, but you can read this now, better than in a year's time.