The FLoB-ATHON will last at least 8hrs-20mins (the duration of the first one) with perhaps some charity fundraiser goals to extend it a bit. Of course, at the end of the marathon I will be pressing F3 live for the first time since May 2015 to see how far we've walked in our Minecraft world!
FLoB-ATHON Twitch Channel: http://twitch.tv/kurtjmac
I hope you're able to make it for a bit. If not, don't worry, the archive will be up on YouTube in its entirety!