Hi theire,
in earlier Times of "ESX" i planned more often to reboot the Hosts.
But to be honest now since "ESXI" i just do the Reboots once making Maintenance for Patching/Drivers/FW/Bios Activities.
The Versions are getting more and more stable per Default, so mostly no Reason to Punch Periodicly Reboots. That's more modern .
Re Upgrade. So i just did red "certificate" problems. i remember from earlier times i had to recreate all certs to an higher Security. So i created for sha-256 with 2048 RSA. i just didn't had that much certificates necessary to change.
So if you still have "MD5" onces > then Vmware Update of vCenter don't let you through . and for Esxi i would recommend to re/install fresh. No Upgrades.
If you're environment is supported for 5.5/6.0, then i would remind for planning to get onto minimum 5.5 ones. As much has changed.
Best regards
Max