This living style would suit my DPs and remove the burden of supporting them in their overly large house from me.
From my POV, I don't really care if it's a poor financial decision. It's their money and should be spent on a comfortable life.
My sister, who is a good person, but lives a long way away so isn't involved in the day to day of it, is worried that "we" will have to continue paying charges after their death, if it doesn't sell.
If it's the estate that would pay, I also don't have a problem with that. If their whole estate is swallowed up in paying for this place, to give them a decent life now that's OK. Obviously it would be better if it wasn't but if that's the worse case, that's OK.
DSis is worried that once the estate is spent, the charges would fall to personally. Can that be true?
So, whilst it will ultimately be DP's decision, I'm comfortable if, worst case, all their money is spent, leaving no inheritance, but I wouldn't be comfortable to think I'm committed to paying out of my own money if things were very protracted.