My husband has had his parents' property in trust to him in their will, drawn up long before MIL had dementia. He doesn't live in the home.
FIL died some years ago so it is now technically part his, meaning that (I think) the LA cannot force sale of the house without his say, and it has no purpose anyway as the value of half a house is nothing. Not sure how much they will eventually be able to claw back when she dies though - they could presumably claim up to half the value of the subsequent house sale then.
To get round this, my husband tied up the other half in a secondary trust (he is a Financial Advisor with specialist qualifications in Elder Care planning, so knew what he was doing here - recommend you seek out someone similar, either FA or solicitor, to make sure you do it the right way). This was only done a couple of years ago, so it could be overridden by the LA in the event that MIL goes into care in a close timeframe to this, as then it could be perceived as deprivation of assets (which essentially it is), but if she stays out for another few years then they might not be able to claim this - though if I understand correctly (and I may well not) there is no "line in the sand" for this. I think the more complicated the financial arrangements, the less likely the LA will be to challenge it, particularly when the trustee is a FA of thirty years who could argue his case better than they could in court!
I think the general rule of thumb is the sooner the better, so you have more of a leg to stand on when it comes to dealing with the LA later down the line...