If a project had multiple sessions, I made a project folder to hold them. I used to work for a commercial music composer who did some pretty large projects sometimes.
That way, I can always hear where something left off without having to find and open the session. There's a folder in iTunes for each project and/or type of project. I bounce down a rough mix when a project is going to be set aside for any length of time, and drop it in iTunes. I keep Excel spreadsheets of projects when they grow large enough - the name, state, and location of each session maybe keys, tempos, and lengths if appropriate a notes field for misc info. I then move the session to the appropriate folder. Sometimes the purpose or stage of development of a piece changes. choral music, with subfolders for original music and MIDI learning tracks.songs written with other people, with subfolders for each partner.instrumental music, with subfolders for different purposes.On my personal partition, I organize by type or purpose of the session. First, I have one partition for my personal projects and another for client projects.
