I wondered why, while at home, when I "woke up" my Rezound, it was in the 4G mode, and then would switch to WiFi. Discovered that when I went to "settings", "WiFi", "Menu", "Advanced", the option to "Keep WiFi on during sleep" was set to "Never". Is this the default setting for the HTC Rezound? I sure wouldn't have selected it. A warning states that the setting uses more data. What advantage could there be to turn off WiFi while sleeping in a WiFi area? I suspect that the "Never" setting is a battery hog, forcing the phone to communicate with distant 4G towers rather than nearby WiFi. I reset that setting to "Always". Time will tell if my battery lasts longer. Checked the wife's HTC Incredible 4G, and the setting on her phone was "Always".
Will report back if I see a significant change in battery life as a result of the change to "Always" (remain in WiFi when available).
If anyone knows why one would want the phone to go into the 4G mode in a WiFi area while the phone is sleeping, please comment.