Life Overview of Alma the Elder, the Younger, and Helaman

I hope that you find the lives of these Book of Mormon Heroes as inspiring as I do! I want to do a better job of knowing the events and timeframes of their lives, and writing this out has helped me a lot. I also give my best guess below for their age at death, even when it isn't totally clear.

Alma the Elder - Life Overview
born in the land of Lehi-Nephi in 183 BC, becomes a priest to the wicked King Noah
148 BC defies King Noah as a young man (age 25) and begs the life of Abinadi
147 BC teaches the gospel in secret
145 BC discovered by the king's agents, flees, founds the city of Helam
121 BC taken by the Lamanite army (searching for people of Limi), heavily persecuted
120 BC the Lord puts the Lamanites in a deep sleep and Alma's people are freed (v23 cracks me up)
120 BC given authority to lead the church by King Mosiah son of Benjamin, governs the church
92 BC his wayward son meets an angel and is converted
91 BC dies at age 82** after seeing his son appointed as chief judge

** Mormon helped us out, and told us he was 82 at time of death. Otherwise, we know that in the Jewish tradition, typically priests were at least 30 years old and married to start their ministry (not sure of my source though). This would make Alma 87 years old at the time of his death. Alma the Elder was never a military leader.


Alma the Younger - Life Overview
born to Alma between 145 and 120 BC (probably in the city Helam, which his father founded)
100 - 92 BC seeks to destroy the church with the sons of Mosiah - meets an angel and becomes converted
91 BC becomes the chief judge
90 BC contends with Nehor
87 BC leads armies against combined army of Nephite dissenters and Lamanites, wounded in battle
83 BC yields judgment seat to Nephihah, preaches the gospel to the Nephites
76 BC contends with Korihor the Anti-Christ
76 BC leads the mission to the Zoramites
74 BC gives his last words of advice to his sons, gives Helaman the plates (Helaman was his second choice - he asked Nephihah to take the plates but Nephihah refused)
73 BC leaves Zarahemla and is never heard of again

If Alma the Younger was born 138 BC in Helam, about 5 years after the city was founded, then he led the Nephite armies at age 45, and was 65 years old when he died. Alma the Younger was engaged in battle and wounded severely in battle 6 years before his death, which could explain the difference in age at death and his father's age at death.

Helaman son of Alma - Life Overview
born
74 BC remains at home while his father and brothers teach the Zoramites
73 BC receives responsibility for the plates from his father
66 BC leads the stripling warriors (War with the Lamanites broke out in earnest 3 years previously)
61 BC war ends, Helaman preaches to the people.
57 BC dies

When was Helaman born?
It is hard to narrow down a range for Helaman's age or year of birth. I wonder if he was born during Alma's rebellious years of seeking to destroy the church. It is hard to imagine him a married man trying to destroy the church, then his sons growing up to lead the church.

Clue #1 - Helaman was "in his youth"
Helaman was "in his youth" as Alma instructed him about the plates. Perhaps this is why Alma preferred to give the plates to Nephihah (see above), who turned down his offer. I take in his "youth" to mean that he was less than 30 years old. However, his younger brothers went on a mission before Helaman received the plates. If they had to be 30 to preach the gospel, I would assume Helaman was more like 35 years old when he received the plates.

Clue #2 - Helaman was an army commander for 5 years
Helaman must have died very young then, only living 16 years after receiving the plates. Helaman never admits that he was wounded in war, but he was very worried that some of his 2,000 stripling warriors had died. I could easily imagine that he was wounded in that first battle and that was part of the reason for his concern. Even if he wasn't wounded in that battle, there are many more ensuing battles that could have taken their toll and shortened his life.

Conclusion
Based on Alma's ministry, Helaman was probably born close to 100 BC, putting him close to 27 years old as the prophet, and 43 years old when he died. This would make sense with Alma saying Helaman was still "in his youth" when he received the plates. Dying young also makes sense for an army leader. The only contradicting factor is that his younger brothers went on the mission to the Zoramites, which I would explain by saying they were acting under the Aaronic priesthood.

 ... but Helaman's age is just an educated guess.  What are your thoughts? Are you surprised that Helaman died so young? or that Alma was so old?