How old will people be in Paradise?

How old will everybody be in paradise and will they grow or remain the same as they were when they first enter paradise? And please can you tell me why? Thank you very much!!! I will really apppreciate it!

Praise be to Allaah.
Allaah has prepared Paradise as a reward for His close friends who obey Him in this world and who are patient in following His commands and heeding His prohibitions. He has placed therein everything that is dear to them, as He says (interpretation of the meaning):

 “(there will be) therein all that inner selves could desire, and all that eyes could delight in and you will abide therein forever”

[al-Zukhruf 43:71]

It was narrated that Abu Hurayrah (may Allaah be pleased with him) said: “The Messenger of Allaah (peace and blessings of Allaah be upon him) said (that Allaah said): ‘I have prepared for My righteous slaves that which no eye has seen, no ear has heard, and it has never entered the mind of man.’ Recite if you wish:

“No person knows what is kept hidden for them of joy as a reward for what they used to do”

[al-Sajdah 32:17]

(al-Bukhaari, 3244; Muslim 2824).

Therefore we believe that the condition of those who enter Paradise will be the best and most perfect condition in all senses, whether we know the details of that or not. Knowing some of these details is something that makes the Muslim more interested and more motivated to do good deeds.

One of the aspects of this perfect condition has to do with the ages of the people of Paradise. There is a hadeeth which states that they will enter Paradise “aged thirty-three years” (narrated by al-Tirmidhi, 2545; classed as hasan by al-Albaani in Takhreej al-Mishkaat, 5634). Ibn al-Qayyim (may Allaah have mercy on him) said concerning this age: “There is obvious wisdom behind this, for it is the most perfect age at which one is most able to enjoy physical pleasures, and the age at which one's health and strength are most perfect.” (Haadi al-Arwaah, p. 111).

With regard to whether they will grow older, there are some ahaadeeth which do not confirm that they will not age. What has been proven from the Prophet (peace and blessings of Allaah be upon him) is that they “will never lose their youth.” (Narrated by al-Tirmidhi, 2539; classed as hasan by al-Albaani in Saheeh al-Tirmidhi, 2062). Whatever the case, it is certain from the principle established above that they will be in the most perfect condition, so they will remain young for ever and ever, and their delight will increase and never decrease, and they will live a good life and nothing will ever spoil their joy.

 We ask Allaah by His grace and mercy to make us, you and all the Muslims among the people of that abode, and to help us to act in accordance with His religion and for the sake of His religion, until we meet Him when He is pleased with us, for He is the Most Merciful of those who show mercy.