You don't level up if you don't open chests

I check out various events, collect items from shops and dungeons, grab little things from the guild and town, send characters to hunting grounds to get chests, and can also craft them. Doing this has helped me collect a lot more than before, and even though I only log in for about the time it takes to do daily quests, I'm gaining 1-2 levels as I approach hidden level 90. Anyway, even with auto-play, the chests often stop when the character returns from a dungeon or when a weapon drops, so it's not a completely idle game.