That's really not all that long for it to start. Have you ever changed the fuel pump? My 01 5.0L EB would take maybe 5 seconds to start once it was hot and let sit for 45 mins or so, but always started quickly when cold. I changed the fuel pump last winter (after it failed) and now it starts w/in 2 seconds or less hot or cold.
Try priming the fuel system by turning the key from OFF to ON a few times to see it that makes any difference. If it does it might be a bad (in-tank) fuel pressure regulator.
