Two things come to mind... The only unforgivable sin is the blasphemy agains the Holy Spirit, which is unforgivable in this life and in the life to come... I look at this in one of two ways, either the life to come means every moment that is futur to now or it is for after we die or are taken to heaven, which if it is the latter than we could sin in heaven... Second thing is that Jesus said to put no thought towards heaven or hell, there is enough today to concern ourselves with. Where is that quote?
I have to recount the words of Jesus to you than... if you do not believen the earthly things I have told you than how is it that you will believen heavenly things?