A: I think that to understand what Mormon meant when he told Moroni that "Charity...endureth forever" as it applies to us, we need to back up a few verses and look at the attributes of charity:
Moroni 7:45 And charity suffereth long, and is kind, and envieth not, and is not puffed up, seeketh not her own, is not easily provoked, thinketh no evil, and rejoiceth not in iniquity but rejoiceth in the truth, beareth all things, believeth all things, hopeth all things, endureth all things.
When Mormon describes these attributes, he is not just describing the characteristics of an abstract principle, nor is he solely describing the attributes of Christ and His life. Mormon details the components of the pure love of Christ to the end that we can learn what it takes to shape our lives and our selves to resemble the life and person of Jesus Christ.
Moroni 7:47 But charity is the pure love of Christ, and it endureth forever; and whoso is found possessed of it at the last day, it shall be well with him.
The whole point of the gospel is to help us to become like Christ so that we can gain eternal life. The crowning principle of the gospel, and the most enduring attribute and quality of Christ's life is charity, and unless charity becomes our most defining attribute and quality as well we cannot truly become like Christ.