@Perky It's worth your knowing, if you're not already aware, that if the node has an RTC, then the RFM69's Listen Mode is obsolete. You can get much higher energy efficiency using the RTC to wake the mcu (which, if properly configured, can take as little as 4us) and having the mcu then manage a similar kind of Listen Mode. That's because, using Joes method, the initial Rx listen window (which simply checks for high RSSI) can be as little as 7us. So, the cumulative energy savings really can be quite significant.
It's for that and related reasons that the new upcoming Moteino, if it happens, pretty much needs to have an energy efficient RTC, or similar standalone timer, if it is to harvest the full value of the recent energy related software developments by folks like Joe and Tom and others.