Ok me and probably many others will play for 30+ hours over weekend and this is ok but please listen few advices. I will not go in great detail because I could talk about this for 30+ pages.
- Do NOT drink any energy drinks. You need to save as much energy for playing and even if you feel more energetic after getting sugar and caffeine kick it is actually only short term and you will actually start loosing energy faster and got tired faster making you go to bed earlier giving you opposite result of what you need to do.
- play with shouters shut and light ON all the time. As is getting dark outside your body automatically going to "prepare to sleep mode" and you will get tired and sleepy even if you not. By having same light level all the time you trick your body out of this.
- make some routine to do some physical work every now or then. This can be stretching every loading time or taking a walk in kitchen to take sip of cold water every time your food buff/guild exp buff run out. What ever you chose siting for 15 h not doing anything else is terrible for you.
- Do not eat any fat, chips, meat or junk food 24 h before marathon and while you playing. Food like this waste lot of energy processing and will make you tired and sleepy. Try to set diet eating extremely small meals but 10-12 times a day things like dry fruit, Indian nuts and light meals like fish and chard or something similar.
So while setting this ways to last as long as possible next thing is if you do feel tired and sleepy and feel like endorphins kick is gone go to bed immediately. Trying to over do your body will fuck you up for next few days and overall you will play less. That said if you wake up by your self even for little bit while sleeping get up immediately because you on end of your REM cycle and on that point you will feel equally rested if you slept for 2 cycle for 3 h or 9 cycles for 13h.
Actually best advice it don't do it don't play it for 18h straight but as I know this wont be case for many of us then just this few advices so you all have as blast as I will have.