The longest it has taken me has been 1 hour 15 minutes, arriving at around 9am. The shortest was around 30 minutes, arriving around 1030am. A lot of it is just luck, rather you get to be the among the last people they let into the first customs hall, or among the first that they let into the second customs hall once the first has been filled.

The American line is after you have already waited in line for a long time, and doesn't take that long. Every time that has added on at most 5 minutes.

I have seen a lot of Americans just go straight to the American picture/fingerprint line (which is supposed to be done after you go through the "foreigner" line where your passport is stamped) and the guards didn't really care... so if you are in a rush, just try that.