Why do firefox addons take several seconds to update?

"One simple solution is to go to Tools -> Options -> Advanced -> Update and Uncheck the auto-update for Installed Add Ons.
Probably the best solution would be to change the extension update interval:
You can do so with extensions.update.interval . It is set by default to 1 week (86400 seconds)"

A fast computer won't get the Internet faster... Maybe the site where the extensions are stored is busy or your browser is doing checks before letting you install an update