I just got my BG-E2N for my 50D today (got tired from carrying 24-70 + 580 EXII in portrait, hopefully I'll still get tired, but a lot less strain on my forearms).
From the manual, it states that "two BP-511As with different charging levels are ok to be used simultaneously", I need advices from real world shooters here. Does two different charged batteries matter that much compared to simultaneously drained batteries? Do they die faster or something?
Also, does keeping the "ON" button on the BG-E2N drain a significant amount of battery life while in transit?