I should have been a little more precise in my last post. I should have said that there would be no motivation to change **in the way that Jesus asked people to change** if there was no difference in the afterlife result.
Now, to break that down a little more:
1) Without a belief in an afterlife of some kind, this whole thing is academic. Of course, there is motivation to change if that change will affect one's state of life in the here and now and one's posterity - but those changes generally are not what is being asked of us as Christians. There generally is a disconnect, for example, between saving money and establishing a trust fund for the kids and giving away all and serving others. There often is a tension between getting ahead in many companies and industries and spending plenty of time with spouse and children. There absolutely is a conflict in many settings between being meek and humble and a peacemaker and climbing the corporate ladder. I'm not saying the examples I've given are mutually exclusive, but they don't mesh easily in many situations. So, for many, it is only a belief that what they become matters eternally that gives them the motivation to act differently than they would without that belief.
2) I personally don't differentiate between the outcomes in this life and the next life when it comes to the value of repentance - and I certainly don't mean to imply that the next life is more important than this one. I think there is NO difference - that who one becomes in THIS life is who one is in the NEXT life. Therefore, I believe this life is "more important" than the next one - since the next one hinges on this one. I just believe that those who posit the existence of a next life won't change if they don't believe it will make a difference - hence, my disdain (and I use that word intentionally) for "easy grace". It says, in essence, that change isn't necessary - so it destroys repentance - so it halts personal growth and change - so it nullifies the Atonement - so it causes the creation to be wasted, if you will.
That is what we call Lucifer's plan.