CDMA 1xRTT (Vision) is not like an analog modem that constantly transmits and receives a carrier that chews up a lot of power. If there is no Vision activity, then very little power is used. Yes a Vision connection does use up some power, but it is not as bad as you make it sound. What drains the battery is constantly checking for email, not that Vision might be connected for longer than necessary.

So yes, "push" notifications where you only get something when there actually is an email for you, would be much kinder on battery life than constant polling, whether or not you break off the Vision connection immediately after checking. So you can simply setup an automatic forwarding of a copy of each email to your Sprint email address (1234567890@messaging.sprintpcs.com) and you will get a notification with each incoming email and not have to bother with polling. Hopefully you have grandfathered or otherwise unlimited messaging