Some lounges have a time limit of 3 or 4 hours, some close for the night. From my experience, no one ever threw me out of a lounge, even if having a time limit.

Yes, airport lounges will ask you to leave once they reach their official closing time, as they must secure the facility and perform overnight cleaning and restocking. Unlike the general airport terminal areas, which may stay open 24/7, individual lounges (whether operated by airlines like the Delta Sky Club or third parties like Centurion and Priority Pass) have strict operating hours aligned with flight schedules. As closing time approaches—typically 30 to 60 minutes before the last scheduled departure of their host airline—staff will usually stop serving food and alcohol and make an announcement that the lounge is closing. In some high-traffic 24-hour hubs like Dubai (DXB), Doha (DOH), or Singapore (SIN), some flagship airline lounges do remain open around the clock, but even these may close specific sections for maintenance. If you have an overnight layover and your lounge is closing, you will be required to move to the public terminal seating or a transit hotel. It is also worth noting that many lounges have a "maximum stay" policy (often 3 hours), though this is rarely enforced unless the lounge is reaching its legal capacity.