I'm working on a big series and it's one I drafted many years ago -- a few times.
It seems like whenever I learned something new as a fledgling writer, I went back and hacked away at this series or at least one of the books in the series.
Last year I decided enough was enough. I was mature enough as an author that I could actually write this story now. But oh, it was hard to give up those old drafts. I was ruthless, though. I went through them all, read the prose (oh, Lord, some of it was so bad), tossed out what I knew wouldn't work and kept a few scenes, etc.
Then I started really writing this series and you know what -- none of what I kept will work. These aren't the same characters anymore. I've learned enough as an author that I realized the way I was using those scenes was for my own enjoyment. They didn't help the plot and they didn't help with character development.
Once again I had to step back and jettison that old work. And it was just as hard as the first time. Someday I hope to re-read some of it (it's safely archived on the D drive of my computer) and maybe -- just maybe -- include some of it in my edits as I do finally prep of this series.
Or maybe I'll just laugh at it all and finally, truly, jettison it.
(more books than you can shake a stick at, although why you'd want to...)