How are maximum times of lounge usage enforced?

[Melburnian1]

All my lounge visits have been without time restrictions, but there are lounge passes one can purchase that specify 'maximum of three hours' and so on.

One way to regulate this would be to only allow a passenger access into the lounge from (say) three hours before scheduled departure as printed on one's boarding pass. When a passenger arrives at a lounge is also affected by when check-in opens, and how quickly security screening and immigration can occur, plus the time it takes to walk or travel by buggy to the said lounge.

But aircraft can run late, and so a user may overstay their permitted time period.

In practice, is this enforced or do staff turn a blind eye, perhaps because it's impossible to remember which users were restricted?

 

[Forg]

There’s usually some electronic form of checkin.
Plus lounge staff can be ridiculously good at identifying people, my wife was being greeted by name by multiple staff when we were in the QF SIN lounge & she’d not been there before …

Likely they normally don’t bother enforcing time limits, but if they wanted to they could.