disable temporary autoconf inet6 address
A similar question on SuperUser prompted me to look into sysctl settings, with the following setting available to prefer the permanent IPv6 autoconf addresses to the temporary ones:

% sudo sysctl -w net.inet6.ip6.prefer_tempaddr=0
Password:
net.inet6.ip6.prefer_tempaddr: 1 -&gt; 0
% 


For ssh sessions that aren't expecting any ongoing interaction, this would make it possible to go to sleep, and wake up within a number of minutes without any SSH connections suffering a disconnect (which would previously happen due to the prior IPv6 address being de-provisioned upon the wakeup from sleep).   (Don't need no mosh!)