White sage

White sage is spiritually most common is smudging rituals, which have been used for thousands of years.
The practise itself has been traced back through many different cultures. 
It is believed the smoke from the white sage purifies the air because it captures the negative energy and the smoke then "ascends it to the heavens'. 
There is no recommended time frame for when you should smudge your home with sage. People usually use there intuition and the way there environment & personal energy feels.