well, odd to say I'd like to check the connection less often than 60 min, basically the same question of yours...

I discovered that setting an interval for connection check makes the device check and really connect (if the flag is set to "connect automatically every connection"). In absence of wlan (or disable), it will connect to gprs every x mins, using auto-disconnect disconnects after x mins, so you have auto email checker!

Maybe that was known, anyway searching the forum long ago found a thread with people saying you could not auto check emails on N900