What does it mean to remember the couplet for a hundred years and be filial for three years?

"Three years of filial piety is easy to be full; This couplet means that three years of filial piety to our loved ones can easily pass, but our thoughts about our loved ones for a hundred years are unforgettable. Children's filial piety and deep memory of their deceased relatives (father or mother) are entrusted in couplets.

According to the rules of couplets, the last word of the first couplet should be written silently, and the last word of the second couplet should be written horizontally. Therefore, the first couplet of this couplet should be "three years of filial piety is easy to be full" and the second couplet should be "never forget home for a hundred years".