Can't say that I have seen this problem with the frequency that you describe. Maybe 3 or 4 times have I needed to fully restart the phone to restore connectivity, over the now 18 months I have had one.

I have mine set in a similar way, and it sits on WiFi at home and work. At home, I don't have e-mail access to my work push account. And every morning, the phone will have connected over 3G and grabbed my work e-mail during my 5 minute commute to the office.