Quick questions regarding the minidungeon event

1. When will the event end? I can't find it anywhere on Nexon's site.
2. Is it advisable to buy 2x drop solely for the event? I'll probably buy the extra tickets in the cash shop, but I won't use any of the remaining 3.5 hours of the card. I got 41 crystals on my first attempt today without it if it matters.
3. Can anyone confirm whether or not mastery books still come from the event, and if so, whether or not they still cost 3000 maple crystals? When I spoke with Noami, she only mentioned prizes up to the Under the Maple Tree.
4. Is the six per day limit reset at midnight PST, or is it reset in 24 hours, like papulatus?

All of this is post-v0.62 by the way.

1) last one lasted 2 weeks, so around that probably
2)well depends how often you plan on running every day, and what items you want, if you average lets say 40 crystals per run, multiply that by x runs per day and 14 for how long the event lasts. If you wont have enough crystals pick up the double drop, then go train afterwards or something.
3)Im assuming so, but Nexon hasnt said anything, and if you read what she actually says, she says to go to the website for the skillbook information.
4) Not sure on this, though I dont know anything that resets at Midnight PST in Maplestory, most things reset at an actual 24 hour mark, quests, bosses, etc.