Further I don't think that immorality=fun. But I doubt that an eternal life can be interesting for ever, and whatever you do, be it absolutely moral or totally immoral doesn't matter - at some point your existence becomes boring.
Of course I can imagine that this doesn't happen but only as it can happen that a person with a certain kind of brain damage can watch the same movie again and again as if it were the first time. But this isn't exactly what I had in mind.
In this sense I have to agree with Mencken who said that "no show, however good, could conceivably be good forever".
It will indeed be interesting forever. You are looking at it from your limited finite mortal human point of view. We humans are so linear ( :-) ) When believers are transformed, they will be given new bodies and they will be made perfect in Christ. There will be no more tears, sorrow, pain, boredom or anything that relates to the fallen nature of this world and this mortal life.