I guess there will be no sin if you get to inherit some portion of the bitcoin stash to your next generations. Because, definitely you will be doing that with fiats and properties then why not with bitcoins. It means you do not need to spend all your bitcoins within your lifetime.
I guess all long-term holders must be planning for saving bitcoin for their grandchildren as well. Because it is already proven that bitcoin is getting more value over the time hence instead of spending all the bitcoins right away, it would be a better idea if we save any little amount of bitcoin now that would become more valuable in future.
It means you do not need to spend all your bitcoins within your lifetime.
I do see it is just a personal preferences. Definitely varies across individuals. And moreover not in all cultures, parents are saving for their children; they just inherit only knowledge and values.