Interesting that you do one session per project - I've experimented occasionally with that, but I ended up in the one window per project, and then break up the work in to 4-8 panes (more or less). Every window gets a name (my new window shortcut requires it) so it's relatively straightforward (for me) to find the project context, particularly as the bash_history is named after the window, and shared between panes (so you can pull the entire work history for a project based on its name).