Publicity for Assisted Suicide

Courtesy of Terry Pratchett and the BBC, a documentary showing the death of a British millionaire in a Switzerland clinic.

I am pretty certain that I agree with Pratchett and the right to die side of this debate, in that I think there clearly are situations in which someone can, in full knowledge of their position and life prospects, reasonably decide that they want to end their life on their own terms, before an illness/whatever does so for them.  I also think that we can probably establish principled reasons for not extending a right to die beyond illness/suffering related cases.  I am not, however, sure as to whether we should attempt to establish these reasons.  I worry that doing so would be overly paternalistic. 

What limitations should there be on the right to die?  Age restrictions spring immediately to mind, because of the popular notion of the depressed teenager for whom it actually would get better if they stuck around. (Side Issue: That link goes to the It Gets Better Project, which is dedicated to helping LGBT teenagers cope with their sexual identity.  A worthy cause, and immediately relevant to this issue, due to the high rate of self harm and suicide amongst this group of people).  But some people of any age would have legitimate reasons to want to end their lives (the terminally cancer-stricken teenager, for example).  So a simple age limit will not suffice, it must be modified by something like the necessity requirement arising from illness/suffering.  We might also worry, as we do for age restrictions generally, that these are ill founded.

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Thoughts?