Once you embark upon the expedition, there are no fail conditions. You can faint as many times as you want, you will be returned to Base Camp each time, and just keep trying! If you reach the wagon at the end of the Everwood map , you will get some special perks and rewards, and more Caravan Points.
Depending on how well the hunt goes, this expedition may be registered as an official Guild Quest, which means if you register it to your list, you can go on it with multiple people! Each large monster you kill during the expedition will increase your chances.
You can store up to 99 Guild Quests, but you can only register ten at a time. If you want to replace one of them, then you will have to delete the replaced quest permanently , so carefully consider whether you need that quest around or not. Once you have registered a guild quest, every time you embark upon it, it will gain levels, which cause it to become more difficult, and as a reward, give you rarer items and Relics. Guild Quests are official quests, so you no longer have unlimited lives.
Level 1 - 30: Low Rank rewards
Level 31 - 85: High Rank rewards
Level 86+ : G Rank rewards