> The one exception would be if I had a long layover.

That's what I did for a day-long layover in Istanbul. I took a short self-guided tour of the city via tram, then returned to the airport in the evening and paid for the lounge until my 1 am flight. It was like 20 Euros, absolutely worth it (this lounge had a shower).

I've taken the freebie lounge access on those rare occasions I have a business class ticket, but only if there is no line. If it's a zoo, what's the point? I can sit in one of the empty gate areas with no one around me until it's time to get on the plane.