If you get the long crank time again, here's something else to try - release the key as soon as you sense it going past the usual half-second, then immediately turn the key again. It may start right away the second time.
That's what mine does. I don't know what it means, it's just something I've noticed and a way to reduce strain on the starter and the engine. Since I got my jeep, it usually takes a long time cranking (like 4-5 seconds) if you just turn the key one time (even after waiting the 2 seconds for fuel pressurization). But if you crank a half-second, let go, then crank again, it starts immediately.
Note: I replaced my engine at 150K miles and the starter around 200K (bought the jeep at 95K), and the starting behavior was the same before and after both those events. So whatever the cause, it's not the engine or the starter - it's fuel delivery, or the computer programming like 5-90 said, or something else along those lines.