That's achieved with Cyclic Sleep modus I assume? A good suggestion, though there are some practical issues in my case.
AFAIK, Cyclic Sleep consumes a bit more than Pin Hibernate, and I really want to make to stretch the battery lifetime as long as possible. Second issue is that the microcontroller will wake up more often than than the XBee in the final version. For example, it measures the temperature each 2.5 minutes, and sends the average value after 20 minutes. All to save as much energy as possible...