First class lounge doesn't close. Due to my own error I booked my flight from LHR to BKK on the 2p flight leaving LHR which had me arriving in AUH about 1am and departing around 7am. I went to the lounge and it was busy when I arrived and asked if any of the 2 private rooms were available. Within 15 minutes the had one ready for me and by 2am the lounge was mostly empty and by 3am I was the only one in there except for a few staff.
About 5am I woke and showered and had a lovely breakfast by 6am with more and more staff arriving. The lounge was still mostly empty until about 630am when it started to get busy with flights coming in.
They were very accommodating in regards to the lounge. Asked if I wanted anything and set me up with water, blankets, eye shades etc.