Mozilla isn't putting a gun to anyone's head and forcing them to upgrade to Firefox 3.5 (such a tactic wouldn't be feasible - we ran the numbers), but don't put it past the open-source browser maker to try and nag Firefox 3.0 users to death.
We suppose if you've gone this long without upgrading, you probably have your reasons why, or maybe you're just an overweight, forgetful gamer living in Seattle ( it wasn't us that said it ). Whatever the reason, Mozilla plans to send out messages to Firefox 3.0.13 users urging them to upgrade to Firefox 3.5 because it's "twice as fast."
Staunch holdouts who refuse to see what all the fuss is about are welcome to ignore the upgrade offer, but will again be reminded in 24 hours. Or select the option to never upgrade, but according to news and rumor site The Register , doing so will only remove the upgrade prompt for "several weeks or months," not permanently.
If the reminders don't bother you, the lack of security updates and patches might. Firefox 3.0 users have until January 2010 to upgrade before Mozilla cuts off support.