I manage 1000+ Windows and Linux servers in an enterprise environment. Unplanned downtime is, to put it lightly, frowned upon.
My risk tolerance level is zero. Obviously yours is higher.
My tolerance is low. I have 2 identical HP Compaq 6000 Microtowers; one is a back-up. The 4 WD external drives have identical data as the HDs.
Kudos to you for being able to manage all those machines.