Of course solar isn't operating at night, but wind keeps blowing.

One way to check this would be to find a wind farm that publishes their output over time. Looks like NREL has some good resources: https://www.nrel.gov/grid/wind-toolkit.html

I'm sure those times aren't common, but we need to have some answer for when they do inevitably occur. The recent Texas freeze was a once-in-a-century event and I don't think many consider that acceptable (and I would think that the no-sun / no-wind scenarios are more frequent than once-in-a-century). I'm sure someone has researched the amount of storage necessary, but the numbers I've heard from articles and podcasts tend to be in the days-weeks range--much longer than 4 hours.

And it's not just the electricity sector where this matters. A battery vehicle uses much less energy that a gasoline vehicle, because the latter has maybe 25% average thermal efficiency (that varies with details, of course). It applies to any industrial process using anything below arc furnace level heat: heat can be generated by heat pumps (compress argon to the desired temperature, extract the heat, then expand the cooled argon maintaining its temperature with low grade waste heat to recover some of the work.)

About the only place it doesn't apply is if the electricity is used to make synfuels (aviation fuel, for example) or in chemical processes where the fossil fuels were used directly (hydrogen for ammonia synthesis).