Firefox has gotten much more stable over recent years in regards to having excessive amounts of tabs open. I can have over 300 tabs open and it's stable (I was using Waterfox when doing this in Windows though).
I have over 300 saved tabs in Firefox on my desktop, and it is stable, but I notice it runs quite a bit slower than when I only have a few open. I really need to start closing some tabs here and there...
It only loads the actual tab when you activate it though, so I don't think all the tabs are being stored in memory, just the ones you activate during a session. I probably actually load about 30 or so during a session, with many more being opened, looked at then closed.
