I said tab but I don't actually use the UI concept of a "tab", though I could by M-x tab-bar-mode, because you're right it doesn't scale very well to large numbers, in my experience

I use buffers (in Conkeror). Buffers are just tabs without the actual tab UI. So unless I'm switching buffers, the only visible UI difference between having one buffer and 2000 buffers is the string "[2011/2011]" in my status-line showing my current buffer number and total number of buffers.

I can press C-x b (switch-to-buffer, I bind to M-a) to show a filterable list of my current buffers (favicon, url, title). I can type part of the url or page title (even when tab is unloaded) to filter my buffer list before switching to one. I can also navigate tabs "spatially" (from tab #2 to either tab #1 or #3) or by recently used (bury/unbury-buffer or switch-to-recent-buffer which shows buffer list in most recently used order) or by domain (next-buffer-same-host) or by whether the buffer is playing audio (switch-to-audio-buffer).

Also, in the vast majority of cases I only access recent tabs near the end of the list. I can press 9 or 0 to go to my second-to-last or last buffer.