How much time does moving to 64 nits buy us? it's likely considerable, but I cant help but imagine a time when we have to address this problem for a third time. It seems to me like a more robust solution is possible.
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Worrying about 64-bit time overflow is like worrying about IPv6 address exhaustion.
And for those following along at home IPV6 is a 128 bit value. ~2^93 is enough to individually address every subatomic particle on Earth.
IPv6 address exhaustion is very unlikely, but it's more likely than some may have thought about.
Only 64-bit of the 128-bit address space was fully utilized, it means the utilization rate is less than 0.0000000000000000055%. And no, it's not a bug, it's a feature. The huge address space was intended to make address assignment, configuration, and routing easier. That is, in the real world, the first 64-bit part becomes the network identifier, and the last 64-bit becomes the device identifier. Ideally, everyone's home, business, institution, datacenter, etc, will get a unique, globally routable 64-bit network prefix.
So no, every subatomic particle on Earth will not get its own IPv6 address. But, everyone of the 7 billion people on Earth can have prefixes for their 263,524,915 personal computer networks.
"12 attoseconds is the world record for shortest controllable time"
https://phys.org/news/2010-05-attoseconds-world-shortest.htm...
After further consideration, the ultimate timestamp would be able to denote any point in time measured in Planck units (10^-44 seconds) between the beginning of the universe and its ultimate heat death in about 3 x 10^21 seconds. Therefore 218 bits should be enough for anyone.