I had read this article previously but it is not targeted at this question
and I am still unsure as to whether the heartbeat interval is defined on a
server or device basis, especially as the article refers to min and max
intervals, imlpying that a range is acceptable.

On a WM5.0 AKU2 device there are similar registry keys, under
HKCU\Software\Microsoft\ActiveSync and in addition their is an
InitialHeartbeat key.

So, the question remains, can someone explain the relevence of the initial,
min and max settings and whether they should be set on the server or the
device?

thanks