Do you know of an Industry Average Data Center UPS Runtime ?

I am trying to find if there is such a thing as an “industry average” for Data Center UPS runtimes. If you work in a Data Center, what is your run time design? Normally, a Data Center would only need to run long enough for the Generator to start in the event of a power outage. In the case that the Generator doesn’t start for some reason – how long will your UPS keep things running?