proper placement of the word either in a sentence

Question

Is the word "either" correctly placed in the following sentence?

Leftover materials either have to be left behind to be destroyed or kept for your own personal use.

Answer 1

That is a placement that many people would use, but a better place for it would be before left:

Leftover materials have to be either left behind to be destroyed or kept for your own personal use.

That uses a more parallel structure. The word either comes just before the part of the sentence that is different in the second half. You can see that like this:

Leftover materials have to be
(either) left behind to be destroyed
(or)     kept for your own personal use.

Answer 2

Another acceptable placement would be this:

Leftover materials either have to be left behind to be destroyed or have to be kept for your own personal use.

Like the previous answer, this works because of parallel structure:

Leftover materials
(either) have to be left behind to be destroyed
(or)       have to be kept for your own personal use.

Answer 3

Recommended usage is that "either" follows the relevant verb, and sits immediately before the contrasts in question. Hence the second suggestion above is grammatically the best - wherein either follows the verb "to be':

"Leftover materials have to be either left behind to be destroyed or kept for your own personal use."