The sweet spot for me is vertical tabs that autohide into a narrow strip of icons until hovered over (like Edge or certain firefox CSS tweaks)

For me, tab location is spacial in my mind, and so many years of having them horizontal makes it hard to switch. Somewhere between 25 and 40 I start having trouble finding things at which point I just close them all and start over. I do use the tab drop-down in Firefox, but mostly to more quickly find things I want to close. Also completion in the url bar to find specific open tabs is quite useful.

I switched back to horizontal tabs because sidebars eat up too much horizontal screen space.

I have the opposite problem: I close tabs too soon, but history solves that.