I haven't had time to use my 4th gen 64GB Touch the last few days, and after three days unplugged, the battery is down to 20% and needs to be recharged. Is that normal? I did leave WiFi on, and I didn't bother to shut down Safari or anything else. What about when WiFi is off? What is the expected "standby" time? FTR, I get at least 3-4 continuous hours use when actively using Safari with brightness at about 70% or so.