If your plant is ready and ripe then harvest it and get started again.
Don’t fuck about with extended darkness prior to harvest etc.
if you have a harvest ready to chop, but can’t chop it all at once then leave it in the dark sure.
keep humidity under 50% and temps above 16C until you’ve managed to chop everything
perosnally I multi strain almost every grow and have plants that finish before others.
extended dark periods are just too much hassle to sort out.