Here is what Irenaeus himself wrote and I base my conclusions nothing but this:

[[[[[They, however, that they may establish their false opinion regarding that which is written, "to proclaim the acceptable year of the Lord," maintain that He preached for one year only, and then suffered in the twelfth month. [In speaking thus,] they are forgetful to their own disadvantage, destroying His whole work, and robbing Him of that age which is both more necessary and more honourable than any other; that more advanced age, I mean, during which also as a teacher He excelled all others. For how could He have had disciples, if He did not teach? And how could He have taught, unless He had reached the age of a Master?

For when He came to be baptized, He had not yet completed His thirtieth year, but was beginning to be about thirty years of age (for thus Luke, who has mentioned His years, has expressed it: "Now Jesus was, as it were, beginning to be thirty years old," when He came to receive baptism); and, [according to these men,] He preached only one year reckoning from His baptism.

On completing His thirtieth year He suffered, being in fact still a young man, and who had by no means attained to advanced age. Now, that the first stage of early life embraces thirty years, and that this extends onwards to the fortieth year, every one will admit; but from the fortieth and fiftieth year a man begins to decline towards old age, which our Lord possessed while He still fulfilled the office of a Teacher, even as the Gospel and all the elders testify; those who were conversant in Asia with John, the disciple of the Lord, [affirming] that John conveyed to them that information. And he remained among them up to the times of Trajan. Some of them, moreover, saw not only John, but the other apostles also, and heard the very same account from them, and bear testimony as to the [validity of] the statement.]]]]]

So there you have it. According to Irenaeus, Jesus reached the age of 50. Some think Irenaeus was saying Jesus was crucified at 50 and not that he survived the crucifixion. For our purposes, I am willing to grant them this because it still proves that Irenaeus deviated from the standard Christian staory to the extent that the Church should have excommunicated him for holding this heretical view--if the story was set but it obviously was not.

However, there is good reason to believe Irenaeus refers to Jesus reachng the age of 50 after his crucifixion because he states, "On completing His thirtieth year He suffered, being in fact still a young man..." This seems to be a reference to the crucifixion. If not, I am not aware what other suffering Irenaeus is referring to.

But either way, Irenaeus held vastly different beliefs from what the Church taught and yet somehow remained in the Church as a Church Father. That could only be because the the Church did not have a set story of the death of Christ yet.

By the way, the reason Irenaeus is so desperate to prove that Christ's ministry lasted longer than one year was simply because the people making the claim say his story was an allegory of the annual cycle of the sun through the zodiac. Irenaeus would rather trample the cover story of his own Church--if they had one--by giving us a 50 year old Jesus whose ministry went on 20 years after his baptism than to admit that his ministry was a year long.