[Project_owners] Initialising an extension once per session

[Brian King]

Hi,

I initialise my Firefox extensions the standard way as outlined here 
(using addEventListener):

http://developer.mozilla.org/en/docs/Code_snippets:On_page_load#Running_code_on_an_extension.27s_first_run_or_after_an_extension.27s_update

However, this is fired for every new browser window. Is there a way to 
make it happen only once per browser session?

Notes:

-> this is not about first run, but rather run per session
-> removing the event listener as in the example does not do it
-> i'd like to avoid using prefs if possible

- Brian