At some point it’s faster/easier to search again than to find a tab among hundreds or thousands.

I probably have between 3 and 20 open typically. Once it’s starts getting beyond that I get pretty anxious to finish whatever has be opening so many tabs, so I can clean things up and reset before moving on to the next thing.

In which browser? Tor, Edge, Firefox, DuckDuckGo or Safari?

I see your stealth ad. I'll answer anyway. :)

Usually one. If I'm actively resarching something, it can go up to a dozen or so temporarily. In that situation, I'll also usually have multiple instances of the browser going to segregate topics. I tend to prefer multiple windows over multiple tabs because it makes it easier for me to navigate and keep more than one thing visible at a time.

Depends. I let the number grow until it's on the order of a few thousand usually (enough to where it's bogging down browser performance) and then I make it a point to explicitly save a Freshstart session and then kill all my browser windows and start over. Right now I have 336 tabs open across 19 windows.