Honestly, I wouldn't mind a 4pm closure if the park is a) really empty and b) has short enough paths to be able to get around easily.
When I visited Alton Towers 2 years ago, I planned in 2 days, to accomodate for the huge distances between some rides. First day was Sunday with (I believe) 5 pm closure and the second day was a 4pm one.
The interesting thing: Sunday was the better day at the park. The attendance on both days was around the same, but they operated their rides on a way higher capacity on sunday. Both stations on Air, double loading station on Oblivion, 4 trains on Smiler, 2 on Wicker Man, Nemesis and even Rita.
The queues were still there, but with some intelligent planning (and one one-time fast pass for Spinball) we got plenty of rides in. And the following monday, felt more like a Merlin park. 1 train service on most rides, resulting in longer queues and way less rides on that day.
We used the time to relax a little bit, but if that would have been our only day, we really would have to have rushed through everything to have a chance to get the creds.
I had a similar experience at Heide-Park last year (June). First day, a sunday saw quite short queues and 2 train service on everything (except Krake and Bobbahn, which ran more). My friends and I really enjoyed that day. Second day, one train on everything except for Colossos, and nearly double the queue times.
I like Europas approach of guaranteeing a decent amount of time, but extending it on a usual basis to accomodate for the visitor numbers. Most days at Europa, even quiet ones, they extended the opening by at least half and hour, usually 1+ hour.