Replying to two emails below.

On Wed, Aug 7, 2019 at 7:27 PM ZmnSCPxj <ZmnSCPxj@protonmail.com> wrote:
> -   Re-vaulting transaction. This is where the magic happens. The re-vaulting
>     transaction is signed during transaction tree setup, before constructing the
>     delayed-spend transaction for the parent vault. The re-vaulting transaction is
>     broadcasted when someone wants to prevent a coin withdrawal during the public
>     observation delay period. The re-vaulting transaction spends the delayed-spend
>     transaction outputs. It has a single output with a script created by running
>     the entire vault setup function again. Hence, when the re-vaulting transaction
>     is confirmed, all of the coins go back into a new identically-configured vault
>     instead of being relinquished through the delayed-spend transaction timeout for
>     hot wallet key signing.

As transactions need to be signed in reverse order, it seems to me that there is a practical limit in the number of times a vault can be used.
Basically, the number of times we run the vault setup function is the limit on number of re-vaultings possible.

Is my understanding correct?

Yes, that is correct. When setting up the vault, plan it "all the way to the end" like next 100+ years. With exponential backoff on the relative timelock values, the total number of pre-signed transactions isn't really that high. With a few thousand pre-signed transactions (more than enough), you can have high resolution timelocks well into the future.

On Wed, Aug 7, 2019 at 4:19 PM Dustin Dettmer <dustinpaystaxes@gmail.com> wrote:
Does revaulting vault up with the same keys, or new ones?
Are they new derivation paths on the same key?

Honestly, no idea. The answer to that might depend on each individual vault user. If the user doesn't want to deal with the expense of managing a bunch of unique keys and other data, then it might make more sense to use the same values and have a small blob that has to be stored for a long time, rather than many different blobs stored in different places to deal with.

- Bryan
http://heybryan.org/