De Wikipedia artigo sobre Thor (basicamente a versão em quadrinhos):
Like all Asgardians, Thor is incredibly long-lived and relies upon periodic consumption of the Golden Apples of Idunn to sustain his extended lifespan, which to date has lasted many millennia.
Na página wiki do MCU , na barra lateral há informações básicas sobre Thor (a versão do filme). Lá vemos:
Age: Over one thousand years.
Powers and abilities:
[...]Thor trained and skilled in the arts of battle, which he has practiced for thousands of years.[...]Superhuman Longevity: Thor, like all other Asgardians, is not truly immortal. It is possible to kill an Asgardian and other beings in the Nine Realms. More accurately, Asgardians are extremely long-lived beings. Thor ages at a pace far, far slower than a human, as he is at least 1,000 or more years old; more than likely, like Loki, born shortly before the last great war between the Asgardians and the Frost Giants.
Quanto a Loki :
Age: 1051-1052
Powes and abilities:
Superhuman Longevity: Loki has the capacity to live for thousands of years. Loki was a baby at the end of the last great war between the Asgardians and the Jotuns, over a thousand years ago.
Quanto a Odin :
Age: Thousands of years.
Powers and abilities:
Superhuman Longevity: Odin ages at a rate that is much slower than that of a human being. Even though he is thousands of years old, he still in very good health, greatly belying his appearance. When he died, he was over 5.000 years old if not older.
ATUALIZAÇÃO: CONTENDO NOVAS INFORMAÇÕES DA WAR DE INFINITY DA AVENGERS
Na Guerra ao Infinito dos Vingadores , o próprio Thor diz que ele tem 1500 anos de idade . (Não consigo encontrar uma transcrição on-line no momento, mas assisti ao filme ontem e ele disse claramente).