At the beginning of every year, I make a new playlist on whatever streaming service I’m using. (Used to be my beloved Rdio, now it’s Spotify.) Every time I hear a song I dig, I add it to the playlist. (I may have stolen this idea from Frank Chimero, but I don’t remember for sure.) I occasionally delete tracks, but for the ones I keep, I let them sit there in the order I heard them. I keep this playlist synced to my phone, and I often just hit shuffle when I’m on a plane or I need to zone out and work.
I’ve done something a little similar. I am using an IFTTT recipe, which creates a new playlist every month and adds any saved tracks to the current months playlist. Along with this I try to make playlists to match the moment, whether it be my mixtapes, year-end playlist, or trying to keep track of the years releases with a playlist, where I save every new album I hear, although this one isn’t always updated frequently.