Keeping the Minolta 5400 flash awake
I am not sure how they are being triggered, but if you put them in wireless mode, they will stay on for an hour. Some flashes will not trigger by the hot shoe when in wireless mode, others will. Try it and see if it works. Also, the 4000AF would do the same. If one of the buttons (the light button, maybe) was depressed, the unit stayed on indefinitely. This may work if the wireless mode does not.
Film is a four letter word