We have MagLites in holders (clips?) by the front and back doors. I have a flashlight hanging under my office worktable. And, one in the garage.
We had a pair of something similar (Coleman, IIRC). While plugged in, they kept the batteries charged. Also had an electroluminescent strip on the front to act as a 24/7 nightlight. In an outage, you could unplug them and carry them like a flashlight.
But, the charging circuit was notorious for cooking the battery pack (nowadays, you could probably just plop some NiMH cells in but this was a NiCd -- not easily replaceable)
Dunno. We've never had an outage of more than ~1 hr. Rough calculation: battery pack is 7AHr @ 24V. So, roughly 170WHr. CFL is 13W yields ~13 hours (assuming 100% efficiency). Guesstimate half that?
No question! As would a smaller (wattage) CFL. But, my goal is not to have to have "special" things to address unusual, infrequent events. E.g., if 6 hours wasn't enough, I'd unplug the extension cord and run it over to another UPS -- that has been *off* for all this time (you have to make sure your UPS will start in the absence of AC line voltage; some won't).
I figure at 4 days, "light" is probably the least of our concerns! :> The point of the propane lantern/camp stove was that I could always "steal" a can of propane from the torch kit, in a pinch. A gallon of white gas (for a lantern) doesn't help me when I need to sweat a joint on some pipes! :>