This is something I've been doing for a while and I find it can bring a lot more opportunities to the table when working on a concept.
A while back, I was working on an LP and my computer died. Luckily I had wavs of most of the tracks from the album (although I was still unsatisfied with them).. I moved on from them onto new things since I did have project files for them anymore, until I tried dropping one of the tracks into my DAW and "remixing" my own work.. Changed the way I produced forever. You are able to give a track so much more depth and intricacy, just as you would remixing someone else, when doing this with your own work. Nowadays I usually get a good structure of a track completed, then start a new project and drop the wav into it, editing and manipulating it to create something more.

A good way to put older or unfinished tracks to use

hahaha that's interesting ! definitely giving it a try~

hahaha that's interesting ! definitely giving it a try~

Can always keep the old project file! I find this method is most effective when used on older/abandoned tracks. Or if working on an album for example, this can be used to spice up the older tracks of the bunch.

I have heard of this, and I feel like I should try it!  You could even make stems of the song for yourself instead of just using the final track.