To rephrase a thought that @echo@lemmy.world said in their reply:
Do you remember what it was like before you were born? Chances are no (if you do, please speak with a scientist to study this phenomenon). Thats exactly what death is like. Whether I live 10, 20, 30, or 100 years longer than 40, to me it makes no difference - I wont be aware of those years if Im dead. Sure, for some those 40-50 years they live may be amazing even, but after youre dead its neither good nor bad - it just isnt. So for me personally (always speaking about my own personal beliefs, and never trying to claim that others should also wish to only live until 40/50) Id prefer to die at 40ish. I don't want children (because i dont like them, dont want the responsibility, and my moral code), I refuse to ever get married, so all my life is is a trip that I try to make as comfortable and enjoyable as possible until it stops being so.
Does that mean I will take matters into my own hands and suicide, either by assisted or other methods? No. But in the hypothetical scenario where one could choose when they die in advance, Id personally choose 40 if asked right now.
And to insert a witty quote, "Death is a lot like stupidity. Its only painful for others". I unfortunately don't rememember who said it.