Check the RAM usage of each tab. My Firefox is constantly open at work, albeit with anywhere from 1-10 tabs, and it never gets slow. Only time I restart it is when Firefox updates.
Firefox
A place to discuss the news and latest developments on the open-source browser Firefox
It's either you need more RAM or you must learn to use a tab group extension. Also, if it gets slow, just restart it.
Simple Tab Groups is a nice add-on.
My personal favourite is Sidebery. It has vertical tabs and easily navigatable via mouse wheel. You can even unload a tab. And has tons of customization options.
I ran into the same issue on my PC.
Dawg I had like ~35 tabs open and hadn't restarted my PC in over three weeks. Fucking Firefox was sucking back 80 gigs of RAM. 80 fucking gigs.
On the bright side all the tabs were still loaded when I clicked through them.
I can't wait for Servo to be finished so I can move away from Firefox, it uses way too much memory.
I'm so hyped as well! Just read their monthly update blog today actually! I'm mostly hyped because it's the first actual new web browser in a very, very long time, and that's just plain exciting!