It depends on what you are doing.
I do programming and I need access to project management sites, communication sites, documetations (language and library) and tools sites opened.
When I am researching the topics I am not very familiar I usually read 4 or 5 sources. So in the middle of developing a feature I have at least tens of tabs.
When it combined with home lab servers, entainments, side readings and related readings I usually tends to end up with hundreds.
Firefox and Sidebery let me do that.
Before that I have tabs opened in 3 or 4 windows each with 20 or 30 opened.