That "sysadmin" sounds like a clown.
If nothing else, do the reboots at "off-peak" hours, whatever that may be for your business.
I'd be willing to be he doesn't test his "updates" on a DEV or TEST server before doing it in PROD.
There is no reason a PROD server needs to be restarted that often at non-standard times.
I'd suggest this "sysadmin" be reported and a suggestion to be replaced with this sort of IT practice.
Wow.