@Wigglytuff123
You questioned my assertion that it is about 18m (12-24) from the point of crisis until the point of death or admission to a care home.
Your grandmother moved in because she wanted to, not because there was a crisis and she needed to. And this is why her stay with you was so enormously prolonged at 10 years.
Absolutely do not let either woman move in with you due to “want” as per your grandmother. Have the option open to you due to need - predominantly your need - for example with ourselves we were lacking in sleep and kids were suffering due to all the time lost in travel and duplicated tasks. Having an option to move in would have been preferable. But again only really viable if you ensure the care package is transferable or two household status maintained (see CAB/solicitor).
The reason you had issues with your grandmother was there was nothing wrong with her to begin with, therefore no social services involvement, nor ability to seek power of attorney (which would allow you to go over her head in relation to DLA/PIP, bluebadge, carers allowance. Although in reality, carers allowance is an absolute pittance; if you work at all you are unlikely to get it and most out of work are better to claim other benefits).
This idea that the government is going to roll out the red carpet and give adequate care to your relatives is straight from an alternate dimension.
Let me be clear. Ideally both of these women will remain in their own home, or at least retain separate household status, that is the ideal solution for all, because then they can access maximum care.
But that is inadequate.
Maximum 5 calls a day, lasting between 10-30 minutes, usually about 15.
There will be hygiene issues, food will be crap so then you’ll have health issues resulting, they may have multiple continence issues or difficulty getting to the bathroom on time, depression due to loneliness, falls in the night.
You will be responsible for overnight care; to get overnight respite is about £200 per night. You will be responsible for managing admin (utilities/forms), home maintenance, washing, organising a cleaner, hospital appointments. And helping them to have some quality of life and interaction with the world.
Some would say there is a moral obligation and particularly if you are due to inherit, it’s very bad form to sit and do nothing.
You obviously hate both of them and wouldn’t mind to see them suffer. Mistakenly you believe that you will sit back with the authorities mopping up the mess, and you think you will manage to avoid any inconvenience to your life… it doesn’t work that way; social services, nhs etc will plague you and you will be the first to be called to take responsibility.
I think the best you can hope for, if your husbands position is to move them in at the first whiff of old age, is to press with him that this is unacceptable but to reassure him you will help adding extra support to LA services in the event of a health crisis. Compromise, or I reckon your marriage is a dead duck.