I tried the update today... and it worked fine, the cache worked like it was supposed to.
I did pause at the point when I was prompted to reboot, and I ran 'id' and
'sudo', and checked that the cache file existed, everything was fine. I swear
I've been doing upgrades every 6 months for 3 years and this is the first time it
retained my creds. But hey, it works and that's what's important. Thanks again.