When is the best time to post Spring Festival couplets?

Twenty-eight and twenty-nine of the twelfth lunar month.

Posting Spring Festival couplets can't go beyond New Year's Eve at the latest, that is, it can't be posted after the first day of junior high school, otherwise it won't have the effect of "saying goodbye to the old and welcoming the new". And after the Spring Festival couplets are pasted, you can't tear them off casually. It is best to keep it for one year, so that the whole year can be smooth and auspicious. When the Spring Festival couplets were posted the next year, the new couplets were directly superimposed on the old ones, indicating that they were getting better every year. For this superposition effect, the stronger the Spring Festival couplets are, the better.