After playing around some more, I've found this out. First, my EVDO stays on permanently once activated as described here:
http://forum.ppcgeeks.com/showthread.php?t=22570
and so I've set some settings around and ended up turning my evdo on ALWAYS using ppchacks. Now if I connect to the internet, I can let my device timeout while I'm connected to EVDO (white arrows) and once it times out, it enters the famous Permanent Sleep pattern I've been describing.