[Adrynalyne]

I think you will find that checking your email every 15 minutes is a bigger detriment to the battery than the EVDO connection staying on.

That said, if you want a timeout, its as simple as a registry edit. I've taken the liberty of making two cabs to do it for you.

One for 1 minute timeout when idle, one will timeout after 3 minutes. If you have any apps keeping the connection active, like a browser, it will not disconnect.