I use it to manage my dev environment with a bunch of sessions.

One for my blog, podcast, 2 side projects, contract work, etc.. I usually have 6-10 sessions. Although I don't use fzf to search through them. The built in leader+s key makes finding and jumping between sessions painless, you also get the benefit of being able to see a preview of what's in the session.

I tend to use one tmux session per project. I usually have 2-3 open for various client projects, one open for my TIL repository, and then I go from there. Within those sessions I tend to have separate windows and panes as a way of organizing any (web) servers and other long-running processes. The 'first' window of each session is usually a split between Vim (where I'm working) and zsh (where I'm executing git commands, running tests, etc.).