MilSim West in the U.S. hosts many 40 hour OPs that go without hitches or hangups with player participation through the entire event. This is because the player participation mixed with a large staff and we'll developed game structure keeps things rolling the entire time.
The biggest problem is in Canadian "MilSim" most people go balls out from game start and burn themselves out by midnight when there might still be 8-12 hours left in the event. Longer events require pacing and well organized structure at a staffing level as well as a command level. Command structures need to be tight to ensure squad rotation is occurring and that their players are not falling to attrition. Forced rest, being properly supplied, using good old team work, and actually doing some real preparation prior to the event is what push the envelope to get people through to the end.
Not to toot the MilSim West horn too much, but they have a required kit list for each team that is given well in advance of the event. On game day they have full kit inspections where you lay all your required gear out for a checklist. People missing these required pieces of equipment/gear simply don't get to play because in the eyes of the game staff they aren't serious enough about doing such a large event if they cannot bring simple things on a list to last them the event. It is a time consuming process, but they have a good staff and they feel it is necessary to ensure they are only letting the truly committed players into the event. I think more stern guidelines like this would at least help eliminate the not so serious players from clogging up a limited roster for an event leaving room for the serious MilSim players to get those spots. Obviously for MSW, they have a very large game staff, the event is much more expensive than the $50-65 events commonplace in Canada, and as such they can afford to have an elitist attitude in requiring these items from each player while supplying everyone with counted, limited ammo as well as MREs and water. While I don't expect any MilSim events north of the border to supply food and comforts to everyone, I think having a list of required kit that each player must have on game day or they cannot play is a start at getting people in the right mind set for these events.
People might say that is elitist, but if we are talking MilSim, that is the elite version of airsoft events, meant for the "elite" players trying to put their skills and endurance to the test. This is not to say that a serious player who has never done a MilSim and wants to try one cannot attend. This is simply a good way at ensuring those newcomers to MilSim know what they 100% must have on game day, as well as what to expect.
Some here may be aware of the Deadfall events Brian here on the forums puts on every fall. Thus last event basically started on Friday evening at about 10pm and ended at 3am on Sunday morning. This event had a small number of players, however nobody dropped out of the event at all. Not one person. The only reason the game did not go until 10am on Sunday is because of the terrible weather and temperatures putting several players in pre-hypothermic states, and this was not due to unpreparedness, simply due to the very harsh elements everyone was playing in, being the beginning of October in eastern Ontario not that far from Lake Ontario. This event saw a tightly ran command structure that ensured the preparedness of every player well in advance of the event, and the event structure was not set around "run at the enemy, shoot some people, die, respawn, start over", it was designed around true MilSim with patrols, skulking through dense brush ten feet per minute, and use of Recon elements that were literally in the field in the pouring rain for extended periods of time. BUT, everyone was prepared for this well in advance and designed their kit around their specific roles, which is something that people just don't seem willing to do in other events. As such this event set the bar much higher in my eyes for the potential of MilSim.
It's the player attitude and preparedness, or lack thereof, that causes long events to fall apart, not the length of the event itself. Sorry, it's just the truth.
Guardians of Asgaard
NO EGO, ONLY HARD WORK
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