It can be summed up by a Star Trek TNG quote "When we die it's not goodbye just good memories"
The question is what is the persistance of memory? (I'm not talking about that melted watch painting by Dali :) )
Even light from stars will break up if it travels long enough. That's why stars that are closer are more visible than similiar stars farther away. Given enough time, even a memory can perish. However, some memories can last milleniums.
Instead of looking for life after death, we should be looking for life during life ;)