@jkandasa Thanks for your response
I already use "aliveCheckInterval" propreties with value 7 (minutes)
(you have create this after my request : http://forum.mycontroller.org/topic/109/best-way-to-check-status-of-mysensors-sleeping-node/3 , many thanks for this)
But my Smart Sleep nodes have a particular way of doing his jobs :
They sleep during X seconds for an number of loop without Smart Sleep (so no heartbeat sended, no wait for response) and after T (threshold) loops , do a smart sleep, then restart his cycle...
For example :
My Node do normal sleep during 300 seconds (X) with threshold 10, so after 10 loop of normal sleep, it makes a smart sleep (heartbeat send + wait 2 seconds).
I do this for battery saving (less wait time).
Maybe I'm wrong and I should always do smart sleep....
Or set aliveCheckInterval to 50 minutes (300*10)