I have encountered a limitation of Firefox fox tabs that I have found a manual way around but seek an auto solution.
I am submitting around 10,000 sites to various search engines using a  START Firefox.exe  .. command in XP's cmd.exe
with Firefox tabs.  Firefox chokes at around 500 tabs and the submission process stops.
Is there any way to clear tabs as they are produced, since the submission process can be a one way event

You may be able to find a utility that can close a program based on its main "Window" name... But then that will require 10000 instances of Firefox start/close

I think you might be able to use Microsoft TaskKill if you check the examples

Thanks - Taskkill Firefox.exe of course kills firefox but the mystery is - with no network log does it kill firefox before it has
done it's site submission. It works with sleep - but how many ms before it is killed  "pause 1" sec works Ok but takes 3 hours
Do you know of any comms monitor that can log the output submissions?  No big problem - just curious

What is the maximum limit of Taskkill Firefox.exe?

I have also encountered similar problem. Often Firefox hangs when we open multiple tab. For me, it stuck even there is only 20 tabs opened. I am surprised to know how you open 500 at a stretch. Which version do you use?