I think that there should be a lot more questions asked before people of ANY age get ANY kind of benefit. My friends who have just graduated from uni have decided that they want their own place, so they've got one, and are paying for it with benefits. There is no reason that they couldn't have lived with their parents for a bit longer, they just "felt like" moving out, which is ridiculous, and what I assume the government is trying to avoid.
But someone of 24 who might have had a job before and is just going through a bit of a hard time should NOT be punished. Nor should an 18 year old who is trying their absolute hardest to get a job, and CAN'T live with their parents for whatever reason.
This "one size fits all" thing that the government has going on is ridiculous, and in my opinion this is part of the reason we're in such a mess.