You asked: What age will we be in Heaven? Will we be 33 years old, the age of Jesus when he died?
The Urantia Book gives us a lot of information about what we can expect in our afterlife. But I have never seen any information that would indicate what age we will appear to be. We are told that we will have a new form that will accurately reflect our true nature. You can read more about this in the section called The Morontia Self, where we learn:
112:6.2 It is difficult to instruct you regarding your morontia personality forms for the local universe career. You will be endowed with morontia patterns of personality manifestability, and these are investments which, in the last analysis, are beyond your comprehension. Such forms, while entirely real, are not energy patterns of the material order which you now understand. They do, however, serve the same purpose on the local universe worlds as do your material bodies on the planets of human nativity.
112:6.3 To a certain extent, the appearance of the material body-form is responsive to the character of the personality identity; the physical body does, to a limited degree, reflect something of the inherent nature of the personality. Still more so does the morontia form. In the physical life, mortals may be outwardly beautiful though inwardly unlovely; in the morontia life, and increasingly on its higher levels, the personality form will vary directly in accordance with the nature of the inner person. On the spiritual level, outward form and inner nature begin to approximate complete identification, which grows more and more perfect on higher and higher spirit levels.
It’s hard for me to imagine what these new forms will be like, and how we will look. As to whether we will have age-related characteristics that we might recognize, like those of a person in the prime of their life as Jesus was, it’s impossible to say. When Jesus appeared in his morontia form, he did appear to be in a similar form as he was in his mortal life. Even so, in many cases, people did not recognize him until he spoke and they could grasp his singular personality. But this would be irrelevant when thinking about persons who die as little children or in old age.
In the passage above, we are told that our morontia forms are “beyond your comprehension.” So, I think it’s safe to say that we will not appear as Jesus did. My sense of that is that Jesus, in order to communicate as he did with material mortals, had to appear in a form that was recognizable to them. But in our new life of morontia existence, we will no longer need to look like we did as human mortals with familiar material bodies. Instead, everyone will have this new kind of form. And we will be recognizable as ourselves according to our personality, reflected as the immortal soul.
In the end, we can’t really predict how we will look, since we have only our material bodies as a reference point. But knowing that our new outer morontia form will reflect our inner personality, it seems like a good idea to pursue as much spiritual growth as we can while we are still here on this world.
Our soul is the immortal part of us that will survive the death of the material body; it gives us our eternal personality identity. So we want it to be in good shape, strong and ready for our next adventure!
112:2.20 The material self, the ego-entity of human identity, is dependent during the physical life on the continuing function of the material life vehicle, on the continued existence of the unbalanced equilibrium of energies and intellect which, on Urantia, has been given the name life. But selfhood of survival value, selfhood that can transcend the experience of death, is only evolved by establishing a potential transfer of the seat of the identity of the evolving personality from the transient life vehicle—the material body—to the more enduring and immortal nature of the morontia soul and on beyond to those levels whereon the soul becomes infused with, and eventually attains the status of, spirit reality. This actual transfer from material association to morontia identification is effected by the sincerity, persistence, and steadfastness of the God-seeking decisions of the human creature.
I would recommend a thorough reading of Paper 112, Personality Survival, for a good comprehensive look at the mechanisms of this next phase of our eternal existence. All of the passages I have cited in this reply are taken from that paper.
Thanks for this interesting question