I was there two weekends ago. The evening waits were around 75-90 min (posted). It took us 60 +15 minutes of 'ride maintenance'.
It feels like to me they are keeping an eye on the park closing time and shutting the line to coincide with that. For instance:
10 pm closing time and a 3 hour wait means line closes at 7pm.
10 pm closing and 1 hour wait means line closes at 9pm.
No hard data, just my perception (and the fact that I got in line at 8pm on a sunday night for 90 min wait).