How long can we keep the 8K before we have to exchange for the 8K X?

For those of us who will opt for receiving the 8K when it comes out, how long can we keep hold of the 8K before we have to swap/upgrade to the 8K X.

From what I have read, we have to actually request the 8K, if we are 8K X pledgers.

This actually applies for all backers who are eligible to receive the 8K. From what I recall the 8K backers will have the option to upgrade to the 8K X ($200), so it would be interesting to know how long before we have to upgrade/swap to the 8K X.

Will it be possible to wait till a later revision?

@PimaxVR @deletedpimaxrep1