http://www.bbc.co.uk/news/uk-33438003

That's her card marked. I wonder what a cost/benefit analysis would look like

I'm all for young adults getting extra care if they are vulnerable but I can also see the system being abused by greedy foster parents. It's a fine line.

Speaking as someone who has been through the Care system, it is not about how long they remain in the system, it is about correct preparation for when they leave the system.
Even if they ate there until 25, the correct care and attention to their specific problems should be addressed with a framework in place to address the issue of the individual eventually having to leave and fend for themselves.

Mark

Agreed. You don't want people 'in the care system' when they're adults, but you very probably do want a system that gives them the same sort of support people from what you might describe as a 'standard' family background get when they first set up on their own. That may be something as simple as advice, good financial recommendations, whatever. But people who have families don't generally get hung out on their own when they're 18, so why do that to kids who have been in care?

Speaking entirely theoretically (I have almost no experience of the care system), surely putting an arbitrary age limit on it at all is going to be unhelpful. People are phenomenally different, and whilst some might be perfectly ready to live independently at the age of 18, others may need help until they are 30. Better to take each person on a case by case basis and decide on what's suitable for them.