I've found that iOS calendar functions work better with push enabled, so I just turned of all notifications, sound, and such for email. Every couple of hours or so, I'll process my inbox, as well as make sure that I'm at zero before bed and when I wake up. During the workday, I process my inbox about every 40 minutes or so, but constantly work out of my "next" folder. The reason for this is that I found out that constantly trying to keep up with my email was preventing me from really getting into projects and tasks effectively. This way, I can still keep on top of email and address actionables, yet I can still perform non-email tasks effectively.