After my youtube video with 40 routers I read some posts on Twitter from @Centronix , @Addizins and @mss7082 about someone who did 45 routers on a Windows machine.
I got curious about what the actual limit would be of the numbers of routers you can run on a single machine. If you add a lot of routers GNS3 becomes very unresponsive when you click and drag new routers to the screen. So far I got 107 routers and the system is running without any problems. I made a video to show you: