Hi, I have my z1 about a month now and discovered a way to save huge amount of data usage and extend battery life. when checking my data usage on phone I noticed "exchange services " was accounting for large amounts of data. In 8 days it used 373 mb. Under email settings I changed from auto (push) feature for continuous checking and loading email -to "check every 10 min.". If someone needs my immediate attention they can text or call. in the next 10. days "Exchange services " used only 15 mb data and there was a noticeable increase in battery life. not sure this setting would not be the default setting or why stamina mode wouldn't include this setting?