Our group doesn't call it Milsim, we call it reenactment. Once you show up, change, setup - game is on. 3 hour patrols through swamps without seeing anybody, stuffing your boots with straw to dry them up afterwards, spending entire weekend without firing a shot, be it airsoft or blank fire, getting lost for hours during night patrols, crap floating around in your zelt after 24 hours of rain, getting up to a "stand to whistle" and running to you firing position every freaking two hours while you expected nice and quite night, fighting for one position for hours and getting things brought up to up from the rear. Pissing off your sleeping CO really early in the morning with loud noise to the point where he wakes up and sends everyone to reinforce/camouflage the damn trench which is already 5 feet deep
People usually stop being part of the action under two conditions - 1. You are really fucked to the point where you cannot function properly for several hours. 2. You need to visit the hospital. Both of those things happened in the past. I guess this is Milsim.