Except most cars don't rewrite their flash every few seconds.
Most modules with flash in 'em are programmed once at the manufacturer, reflashed once or twice during assembly, maybe reflashed once more at the dealer before delivery, and that's it. Maybe again post-sale if there's a recall or TSB or something that can be fixed in software.
Flash quite happily lasts 25+ years if you don't abuse it far beyond any flash manufacturer's wearout specs. Go figure!
If you look at airbag module teardowns there is a giant capacitor, but this is used to fire airbags in the event the vehicle's power system is rendered inoperable prior to deployment.
Most manufacturers’ datasheets specify 20 or less years of data retention (even when powered on). This might seem like random sufficiently large number, but there really are devices made in mid-90’s (notably early FastEthernet cards) that do not work because they lost contents of their configuration EEPROMs.
Most modules with flash in 'em are programmed once at the manufacturer, reflashed once or twice during assembly, maybe reflashed once more at the dealer before delivery, and that's it. Maybe again post-sale if there's a recall or TSB or something that can be fixed in software.
Flash quite happily lasts 25+ years if you don't abuse it far beyond any flash manufacturer's wearout specs. Go figure!