Given that this site is dealing with the theories and work of David Rohl, perhaps I should take this oportunity to promote my own theory concerning the length of Amenhotep III / Akhenaten's co-regency:

Co-Regency

By working backwards with the dates available for the pharaohs of the 18th Dynasty, it is possible to estimate a date on which it was traditional for the eldest son of the ruling pharaoh to become joint ruler with his father. The dates below refer to the kings whose age at death is known.

Parentage of Tutankhamun / Smenkhkare

If Tutankhamun and Smenkhkare were the sons of Amenhotep III, what age would Amenhotep III have been to father them, and therefore how long would the co-regency have lasted between Amenhotep III and Akhenaten.

Smenkhkare reigned for 1 year (2 years maximum)

Tutankhamun was 8/9 when he came to the throne.

Which means Tutankhamun came to the throne 1336BC, and therefore was born 1344/5BC.

If Amenhotep III died in 1345BC (for example) then the co-regency would have lasted 12 years (a date which coincides with the Durbur of Year 12 of Akhenaten, a possible celebration for Akhenaten becoming sole ruler of Egypt).

Destructions of the Tombs

By studying the royal tombs left by the people of the Amarna Age, it is possible to perceive, perhaps, a certain pattern to the destruction inflicted upon these tombs and maybe more importantly the owners of these tombs. Of the kings identified with the Amarna period only Tutankhamun has survived more or less intact. Could this be down to chance, or was there a concentrated effort on the part of the 'Pro-Amun' supporters to erase all mention of the Aten dynasty. A look at a summary of the facts may now be useful:

1. Amenhotep III. Tomb KV22. Although the tomb had been robbed in antiquity, the mummy of Amenhotep III was in the cache of mummies found in 1898. Which confirms that the mummy of Amenhotep III had survived into the 21st Dynasty - therefore the mummy of Amenhotep III did not suffer at the hands of any vegenful fanatics.

2. Queen Tiye. Although connected with the Aten cult through her son, Tiye has been spared any hatred by the Amun supporters. There appears to have been no defacing of her image - even on the Atenist Golden Shrine from KV55. Her mummy again survived into the 21st Dynasty to be reburied in the same mummy cache as Amenhotep III. There is a theory that Tiye was removed from her original tomb in Amarna, placed first of all in KV55, and then reburied with her husband in KV22 - which suggests a certain reverence.

3. Akhenaten. The heretic - the main focus for anger when Amun returned to power. The Royal Tomb at Amarna defaced leaving hardly any evidence showing the reliefs, all funerary furniture destroyed - including all ushabti and the sarcophagi. There are some theories, however, that claim Akhenaten's mummy was moved to the Valley of the Kings when the Egyptian court moved back to Thebes, the evidence for this does seem somewhat insubstantial. The probable scenario saw the mummy of Akhenaten especially, maybe Nefertiti's and their two daughters, pulled from the tomb and destroyed so as to deprive the Ka of the dead peace for eternity. Horemheb then set about annihilating the name of Akhenaten and his queen Nefertiti.

4. Smenkhkare. Possibly buried at Amarna, more probably Thebes. His remains were discovered in a ransacked KV55, his mummy placed into a coffin which had all the traces of Smenkhkares name erased. Also much of his funerary equipment was usurped and used for the burial of Tutankhamun.

5. Tutankhamun. A hasty (?) burial, which had funerary goods supplied from many already deceased members of the royal family, including Tiye, Akhenaten, Nefertiti, Smenkhkare and the Amarnan princesses. Although Horemheb later replaced Tutankhamun's name with his own on the monuments of Egypt, Horemheb did repair Tutankhamun's tomb when robbers broke in - something which Horemheb had not done to other members of the Amarnan court.

6. Ay. Not long after the burial of Ay, his tomb KV23 was totally destroyed - his sarcohagus smashed, his name erase, his mummy probably destroyed and his figures hacked out. Horemheb also replaced Ay's name with his own on all monuments built by Ay.

After studying the destruction Horemheb vented upon the members of the Royal family who had anything to do with the Atenist period, a major discrepancy surfaces:

If Hormeheb / the supporters of Amun destroyed the tombs and / or the mummies of Akhenaten and Ay, why not the mummy of Smenkhkare (especially of they had taken the trouble to vandalise the tomb and deface his coffin) and why not vandlise the tomb of Tutankhamun?

Perhaps it comes down to parentage. If not only Akhenaten but also Smenkhkare and Tutankhamun were the sons of Amenhotep III (and Queen Tiye), so that the family tree looked like this:

Akhenaten dies and is buried with his family in the Amarna Royal Tomb.

Smenkhkare dies and is buried possibly in Thebes after beginning the movement back to the worship of the old gods.

Tutankhamun dies and is buried in the Valley of the Kings.

Ay dies and is buried in the Valley of the Kings.

Horemheb becomes pharaoh and takes his vengeance.

Akhenaten the heretic loses his name and his figure is hacked out denying his Ka any identity.

Smenkhkare was a co-regent of the Akhenaten and so loses his name and identity, but as a son of Amenhotep III and Tiye keeps his mummy for his Ka to inhabit.

Tutankhamun although still a child of the Amarna reign loses his monuments to Horemheb but no more than that, Tutankhamun must be a child of Amenhotep III and Tiye, if he were a child of Akhenaten surely his fate must be the same as Akhenaten or Smenkhkare.

Ay was the father of Nefertiti, he was a supporter of the Aten, he had a tomb built at Amarna, he had no true connections to royalty only that Queen Tiye was his sister.

Horemheb then changes history by claiming that the kingship of Egypt passed directly from Amenhotep III to Horemheb. Amenhotep III and Queen Tiye were leaders of Egypt during a period of immense power for Egyptians, what followed with the Amarna period in terms of its empire - was a disaster. So, Horemheb destroyed the existence of the people most closely associated with the Amarna period, but the other sons of Amenhotep III and Queen Tiye (Smenkhkare and Tutankhamun) were given some respite, they kept their bodies for their ka, and in the case of Tutankhamun kept his tomb as well.