Not sure the issue is always down to age, I think there is an element of ability, wasn't there a young rugby player in his early 20's who went to Dignitas as he didn't want to continue his life as a paraplegic, but the concern was the prosecution of those that assisted him getting there.
There does need to be checks & balances in place to stop greedy children getting their hands on the inheritance, or the Care Home carting a resident off due to rising debts, but in principle it should be available. We need the debate now as it will take 10-20 years to get anywhere