Why did God allow Adam to live 930 years after his act of disobedience in the garden of Eden

For the same reason that He allows anyof us to live at all: that He is very patient.  God warned Adam that death was the price of disobedience.  He didn't say how long it would take. 

My question is why God allows atheists to exist, considering the damage they have done to the planet.

Well,This was the tragic start Adam gave the human race.

After sinner Adam’s expulsion from Eden he lived to see the murder of his own son, banishment of his killer-son, abuse of the marriage arrangement, and profanation of Jehovah’s sacred name. He witnessed the building of a city, the development of musical instruments, and the forging of tools out of iron and copper. He watched and was condemned by the example of Enoch, “the seventh one in line from Adam,” one who “kept walking with the true God.” He even lived to see Noah’s father Lamech of the ninth generation. Finally, after 930 years, most of which was spent in the slow process of dying, Adam returned to the ground from which he was taken, in the year 3096 B.C.E., just as Jehovah had said.—Ge 4:8-26; 5:5-24; Jude 14) some of much today.

Atheists have prevented contraception, jailed Galileo and tortured me to death. It's only my locked chastity belt that saved me.

Adam died spiritually the moment he sinned. He died physically years later.

Everything was perfect and he was created by God's hand and he has been close to be creator!

Think if everything was perfect what kind of sickness or virus had to be developed or how much the human body had to learn to the new fact that it's going to perish? Adam was the most perfect human ever and not wonder why he lived such a long time.

You can see in countries where it's not healthy or education the life expectancy it's lower! and in wealthy countries and well educated it's double!

So just think about the number or sickness, bacteria or virus had in that time? how men's body was perfect? the man just ate natural food in that time because men started to eat meat just after Noe after the big flood when the animal came out of the arch! and then you can see the perish in years after it.     

You can see that he said in Genesis that he ate the fruit of knowledge of good and bad and God protected the tree of life so the man wouldn't eat and live forever.

We die to don't carry forever the curse of Adam! the knowledge of good and bad that makes us obligated to life good and evil stuff in this life. So we can come back to the original state of purity without knowledge of bad ! because if we know bad!! we will live evil too.... This is since the start when Adam choose to have it and then all his seed too.

God didn't want him to life forever eating the tree of life after eating the taste of knowledge and live forever knowing evil and committing evil... if it's not him his seed! his sons or family because since you know bad or good you can choose to live or be one or other! thank God that we don't live forever in this crazy world with amazing and good things but also with so much suffering!