DO NOT LEAVE THE MEMORIAL TABLETS OF THE DECEASED ON THE OFFERING TABLE FOR A PROLONGED PERIOD
Question: During Ching Ming Festival or Dong Zhi (Winter Solstice), should we place the memorial tablets of the deceased on the offering table throughout the day or should we put them away once the prayer ceremony is over?
Answer: Generally, you should put the memorial tablets away once you have finished offering your prayer; do not just leave them there throughout the day. Once you have set up the tablets on the offering table, you may offer incense, prostrate, perform recitation, and prostrate again after offering Little Houses. Once the incense has burnt out, you may put them all away.
It may spell trouble if you leave them there the whole day. Firstly, the spirits of the deceased may not have much time to visit you that often anyway and secondly, in the event they leave, there’s a chance other foreign spirits might come over.
Source: Master Jun Hong Lu’s Discourse (Question 42), 15 July 2012