Mythic lockout

Ok so basically we killed Mythic Silken Court tonight and have Christmas break now.
We want to keep the 7/8 lockout but in the next 2 resets people want to pug or do reclears for the first 4-6 bosses for vault whilst we’re not progressing.

Am I right in saying that if I hold the lockout on an alt and extend it each reset it will keep the 7/8M lockout until the new year and we’re back ready to progress and everyone else can be free to do 2/3 weeks of reclears in between?

This is correct, yes. In the same way someone who is benched for Ansurek could pug 4/8 for a week then rejoin extended prog a week later if they needed to fill a spot.