What is the effect of operating an electrolytic capacitor beyond the rated temperature?
It is not only about ambient temperature, but the actual operating temperature of the capacitor, which includes temperature rise due to internal heating from ripple current and ESR.
It is true that capacitors have a certain lifetime guarantee at certain temperature, but in general that rating is already given at the maximum operating temperature, and thus it would be invalid to estimate the lifetime at temperatures above it with the same formula, as the component would be used outside the rated operating tempetature range so none of the parameters would apply any more.
Panasonic has an application note about this, and it also says that if operating temperature exceeds the upper limit, it will result into rapid deterioration of electrical parameters  and irreversible damage to the capacitor.
So no, this rule cannot be applied, because it would require using the capacitor outside nominal operating conditions, and these have other ways to effect the lifetime.