Thanks Mark.
The EPHeartbeatInterval is already set to 20 minutes and suppose I could set this much higher but I think this would just delay me finding out there was a problem because the heartbeat missing errors would appear to be bona fide in that the EP's have stopped logging into the event servers and genuinely need restarting before they start processing jobs again:
[17:34:09.2802] [1] EP #7 heartbeat missing, appears busy. kill -9 1394 to restart.
[17:34:09.2809] [1] EP #2 heartbeat missing, appears busy. kill -9 1389 to restart.
As I said to Steve C, I suspect it is a problem with Autosys 4.5 running on Solaris 10.
Regards