Welcome to the never ending riddle......Electro caps suffer "higher leakage current" when powered up after a "certain time" in storeage. This leakage current reduces the longer the electro cap has a decent amount of voltage on it. (eg near rated voltage)
...for any particular electro cap...to try finding exactly how much leakage current would flow , and for how long, is almost impossible.
....The datasheets and app notes seem very unclear about this whole issue......i read one app note that said that caps should be taken out of storeage every year and get rated voltage applied to them via a 1k resistor........this then stops high leakage currents.
Electro caps arent date coded...so with any cap, youve no idea how old it is and therefore how leaky it might be if you put it in your product.
I must admit all the electro caps that i see, even after 2 years in storeage, the leakage is said to be not that much, so why they say its a problem i dont know.....the leakage seems never to be more than a few mA......so i cant see why its a problem....maybe it was a problem in the old days with old caps.
I understand your question though...finding the truth on this is very difficult.