User blog comment:B214/Question and Answers 6/@comment-118.172.205.177-20160711144501/@comment-26345952-20160711150227

To be honest, nobody knows the difference between the complete JD and the incomplete JD. Ishibumi wasn't clear in that department.

But, as far as I know, one can say that Vali's JD is complete. It does not mean that it is permanent. Vali can have some control over his JD because he temporarly uses his devil power as a sacrifice over his life and sanity.

The incomplete form still has the same drawbacks as the complete one, but it is never mentioned why is it incomplete. The only thing we know about the incomplete state is that there is a chance that it could break in an instant or use the the whole lifespan of the user until death (same as the complete JD if the user loses his/her sanity).