I agree too—

Though I would point out here that at some point in the future we may find that we need to upgrade cryptosystems for security reasons... and that if we don't _eventually_ deny the spending of coins sent to the old insecure system then we could well find that enormous deposits of zombie coins suddenly appear due to cracking and that their rapid unexpected introduction into the economy is very much not what anyone signed up for and could be disruptive.   So it would make sense to sunset insecure transactions.

Someone arguing for regular long-horizon sun-setting, instead of just a one time event, might have a lot more success arguing it at that time.  In particular, it would be much less bad if you know _in advance_ that you will have to heart beat your coins once a decade, then it would be to find out later that cryptosystem breaks mean you'll have to do it.