"Chess goes for how long?"

When I regale juniors about stories from the Olympiad, one of the show stoppers is how long the games last. When I tell them that I have played games that have gone for 6 or more hours, they simply don't believe me. I can hardly blame them, as for most school chess players, 15 minutes is the standard time control, and even then it is a rare game when all that time is used.
On the flip side are the games that finish in no time at all. Again this comes as a little surprise to them, as they assume that at that level players don't make as many mistakes, but at least the time used makes sense.
I have used the following game as an example, as it is the shortest decisive game in an Olympiad, although there was a 1 and half move draw in a more recent one. The story that goes with this game was that Combe had played a far,far longer game in the previous round, and was quite tired from the adjournment session.


Combe,Robert Forbes - Hazenfuss,Volfgang R [A43]
Folkestone ol (Men) Folkestone (3.4), 1933