XBEE ATEA incrementing without sending

I have an XBee Pro (XBP24-AWI-001) that just sits listening to data packets being sent to it by other XBee Pros(XBP24-AWI-001)
I keep checking the EA parameter and find it is constantly growing, even though the XBee is not being told to transmit anything.
Is there a reason for this?

Firmware is 10EC

This problem is the same issue as my other question (solved)