Outlook Add-In performance issues?

Hi,

Hopefully this is the right forum to ask this question. I have a
large client that has been experiencing performance issues with their
Outlook clients when using a large amount of Outlook add-ins/plug-ins.

Is there a best practices for the amount of add-ins to use? e.g. a
maximum of?

Does anyone have experience with the Symantec Corp 10.1.x (I believe
that is version) plug in for Outlook? Everything seems to work fine
with Outlook under certain circumstances (small emails) but then when
the inbox is full of larger emails and ones with attachments
performance drops and then if I load another COTS Outlook plug-in
performance dropped to where Outlook is unusable. I ran process
explorer and saw that the drain was all I/O. I then ran procmon to
see what outlook was doing and Outlook was extrememly busy reading
images from disk. The easy solution is we remove the plug-ins but
that is not our decision.

How does Outlook work with Plug-ins? Are the items read from memory
or from disk? Are there performance gotchas? Advice?

Thanks,

Nate