Though i still dont have the chance to use the N97 but learned few things with these kind of hardware which are mostly user problems.

a) Always keep the network spex as per the factory. (cell info - Off, Network selection Auto)
b) Always keep the B/tooth off unless required.
c) Always keep the wifi off unless required.
d) Always keep the GPS setting non auto search.
e) Always use the original memory stick.
f) Always be carefull not to discipate the static charge on your memory stick (donot touch the contact points)
g) Always keep the bios/Operating system refreshed.
h) Always try to store the add on programs/pic/music on the add on memory.
i) Never install third party softwares.
j) Never leave your handset in the high temperature (40+)
k) Try to avoid the hardware to be exposed to humidity as well.

Keep a watch on the Nokia web page for any recall notice :-)

These hardware are everything BUT not just the phone so the management has to be accordingly.

Good Luck!!!