30 DAYS! I agree with that cuz I either mine, stay in side, or survive the night ( and like NEVER die)
PLUS I am playing Herobrine's Mansion and am fighting the skeleton king WITH THE DEMONIC SET and never died
I got 20 days but the thing is I am kinda like a morlock when it comes to minecraft.
I would climb down the super long ladder in my base to the underground portion wich is 95% of it, use my passcode sequence to get into my control bunker, pull the lever that collapses the ladder shaft and all additional secret entrances, and live of of my under ground tree farm wheat farm grass reserve cow breeding pen chicken breeding pen pig breeding pen pumpkin farm melon farm carrot farm potato farm and hostile mob looter.