As per my other comment on this thread, you can intentionally decrease the lifetime (aka MTBF) by running the part at 10 or 20% overvoltage, in addition to extreme temp, to create a corner case and stimulate premature failure in reasonable amount of time. 20% overvoltage won't kill the cap, as any part has absolute maximum ratings well beyond what the spec sheet says. Even bad caps have some degree of guard band, else they would never leave the factory.