1) There is a difference between meaning and purpose, and I think the answers we normally hear about the meaning of life generally deal with purpose instead of meaning. My own answer to the PURPOSE of life would be "to perpetuate the species of 'God'" - or, on a personal level, "to become like God". I then would clarify that the purpose of this mortal life is to learn lessons toward that end which only can be learned in this type of setting - to experience things only this sort of world can provide.
2) On the other hand, the MEANING of (eternal) life, I think, can be summed up similarly as something like, "a state of existence that allows for change and growth". Humanity simply is one of the manifestations of life - more advanced than intelligences and spirits and animals and plants, but less advanced than resurrected beings, ministering angels and exalted beings. The main distinction, therefore, in the "meaning" of life for mortal (wo)man, is our place in the evolutionary process of becoming godlike - that we literally are spirit children of God , whereas other forms of life observable to us are not. (Whether they ever will be is open to debate, since we know absolutely nothing about the actual process used to create spirit children other than that they are created from "intelligences", but in their current state they are not "children of God".)
3) I think the Mormon take on these questions is radically different than any other Christian take on them explicitly because our very view of "life" (including Godlike life) is so radically different. The Mormon perspective is much closer to the Buddhist concept of a reincarnative journey toward universal oneness than the isolated and stagnant condition taught elsewhere - and that fundamental disagreement makes our answers to these questions incomprehensible to most who view life itself in such starkly different terms.
4) I don't think Mormonism has a "four minute answer" to the question of the meaning and purpose of life. I think we have about a "four second answer". It's the explanation of the answer that takes exponentially longer, in my opinion, since the answer itself is so counter-intuitive and illogical to most people that they simply can't understand it in its simplicity.