Even though it's not stated or heard if somebody survived the total of 100days yet but the best advice I can offer possible is listed below.
Keep you and your squad well supplied with all necessary items (bullets,wood,sticks,iron,gold,coal etc)
Listen to sounds such as skeletons, zombies, dragons and demons so you can kill or avoid them
Build a house (4x5,3x6 or 10x10 the first number represents length and the second number is width) upgrade the structure once a week or once a day
Endurance mode difficulty starts to climb each day neither that or it basically starts off hard.
Remember you have to play 10days in endurance exit and repeat the process till you earn the in-game achievement.