I am new to the world of tablets... Had my transformer for 3 days now. Is it recommended to shut down when not in use? Or can I just leave it in sleep mode? Last night battery was about 75% and I left it in sleep mode. This morning I noticed a lot of the battery had drained, and the screen was flashing the ASUS logo every 2 or 3 seconds. Tapping screen had no effect. I had to hold the power button until it started up. Just wondering if this is normal or not?