If tmux is local, the reboot is going to kill that too. There are ways to re-create your windows/panes automatically after reboot, but they come with caveats.
iTerm 2 can do that and even restore running processes. In my experience that feature works well enough.
I was going to recommend `tmux` as well. It won't help for _local_ terminal sessions but running `tmux` on any remote hosts has saved my bacon more times than I can count.