Should I leave the airport?

A gap between flights that is too long to sit in and too short to relax about.

I have a layover. Subtract the real overheads from my gap: immigration both ways, security again, bags, the journey each way, a safety margin. Tell me the usable time left.

Then a verdict, leave or stay, and a hard turnaround time. Treat transit times as estimates and tell me exactly which visa and transit rules to check myself.

Airport, arrival and departure times:

During and after the trip. Layovers, days that fall through, what is worth doing nearby, and writing it down afterwards.