Death is like life : a part of the evolutionary process. Actually the creation itself evolves through the process of life and death of its constituents. So it's the creation as a whole that evolves through life and death cycle of its constituents. Everything that has life should come to an end at one point or other and help the creation evolve.

If a thing that cannot die continues to suffer and long for death. It is well documented in the movie pirates of Caribbean when hector barbosa and his crew long for death.

A thing when dies simply ceases to exist individually. If it wants to live forever it becomes greedy and the greedy is evil. So, it comes to a simple logical end that either something cease to exist individually at some point or become an evil wanting eternity and keep suffering.