Praise be to Allah.

Allah says (interpretation of the meaning): 

“Whatsoever is on it (the earth) will perish.

And the Face of your Lord full of Majesty and Honour will remain forever.” [55:26-27] 

Ibn Kathir (may Allah have mercy on him) said: Here Allah tells us that all the inhabitants of the earth will perish and die, as will all the inhabitants of heaven, except for whomsoever Allah wills, and nothing will be left except His Noble Face, for the Lord does not die, rather He is the Ever-Living who will never die. [Tafsir al-Quran il-‘Azeem] 

Al-Bukhari and Muslim narrated from Ibn ‘Abbas (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) used to say, “Allahumma inni a’oodhu bi ‘izzatika la ilaha illa anta an tadillani, anta al-hayyu alladhi la yamoot wa’l-jinn wa’l-ins yamootoon (O Allah, I seek refuge in Your glory, there is no god but You, against being led astray, for You are the Ever-Living Who does not die, but the jinn and mankind will die).” 

With regard to your questions about where they are buried, whether the funeral prayer is offered for them and how long they live, these are matters which are concealed from us. Allah says (interpretation of the meaning): 

“And of knowledge, you (mankind) have been given only a little.” [17:85] 

The Muslim should strive to learn more about that which has an impact on his own behaviour, such as knowledge of Allah, His names and attributes, what he is obliged to believe in and knowledge of the rulings of sharee’ah (Islamic law). He should avoid delving deeply into matters which he is not required to know and in which there is no benefit. I ask Allah to grant us beneficial knowledge and righteous deeds.
And Allah knows best.