What is the life expectancy of a Hobbit?

No official answer exists from Tolkien, as far as I’m aware, however it’s not as long as you seem to think.

Based on the lengths of time known Hobbits had lived for and when they died, Emil Johansson from Lotrproject.org did an analysis and found the life expectancy to be around 96.8 years. Quoting be page:

When interpreting these numbers there are a few things to remember. The Hobbit lifespan of 96.8 years is most likely a very good estimation. There is a relatively large and well-documented sample size and most of them died from natural causes. The average lifespan of a Dwarf is 195 years which is a bit lower than one would expect considering that the age of oldest Dwarves exceeds 250 years.
_{Middle-earth in Numbers}

The total data set for the Hobbit numbers includes 246 Hobbits total, 172 Male and 74 Female Hobbits.

Bar chart of life expectancy:

Life length distribution, by race:

The question is flawed.

Today, the average human life span is 77.5 years according to the WHO, which no doubt includes populations with widely varying life spans.

When Tolkien wrote in the late 1930s and the 1940s life expectency for men was closer to 60 years according to the comment by James K.

Today, the legal age of majority is set at 18 in most legal jurisdictions. So today, the legal age of majority is about 0.232 of the average lifespan. When Tolkien wrote the age of majority was 21 in the UK and the USA. And Tolkien was an expert in medieval languages and literature, and thus learned a lot about medieval history.

In Medieval England, the age of majority for males was set at 21 years.

During the mediaeval era and the era of feudalism, in England the age of majority for males was 21 and for females 14 if married and 16 if single.1 The attainment of such an age was usually referred to as being "of full age". Thus wardship for males ended at the age of 21, on the obtaining by the ward of a "proof of age" writ, issued after a Proof of age inquisition had obtained evidence from a jury of witnesses. Until that time a ward could be forced to marry a person of the warder's choosing, often his own child, and the resultant progeny would inherit the property formerly subject to the wardship at their father's death, usually regulated by the marriage settlement.

https://en.wikipedia.org/wiki/Age_of_majority_(England)#:~:text=The%20age%20of%20majority%20in,cigarettes%20and%20have%20a%20tattoo.[2]

I don't know why the legal age of majority was so high in medieval and early modern England, except that managing the wardship of minors who had property was a relatively profitable business.

So Tolkien probably knew that in the Middle Ages, when the age of majority in England was set at 21, the most common age range for men to die of natural causes was probably between 50 and 60 years old, thus making the medieval age of majority about 0.35 to 0.42 of a lifetime (a lifetime for those who survived their early childhood, that is. Most people born in the Middle Ages died when they were children). So 33 years, the Hobbit age of legal majority, would be about 0.35 to 0.42 of 78.57 to 94.28 years.

Tolkien wrote that Hobbits lived to be 100 as often as not, and Edlothiad's answer links to a study which shows that the known life spans of named hobbits average 96.8 years. So if Tolkien was trying to give Hobbits the same ratio of age of majority to total lifespan as the medieval English had, his math was only slightly inaccurate. Certainly his arithmatic was a lot more accurate than if he had been trying to give Hobbits a ratio of age of majority to total lifespan equal to that of 2020 persons.

I note that in 2020 the average life expectancy is about 77.5 years, and the 10 oldest living persons on August 30, 2020, were 115 to 117 years old.

https://en.wikipedia.org/wiki/List_of_the_oldest_living_people

115 is 1.483 times 77.5. The Old Took's age of 130, unassisted by the effects of The One Ring, is 1.342 times the average Hobbit life expectancy of 96.8 years, so Tolkien wasn't exaggerating when he made the Old Took exceed the Hobbit average by that much.

Also see here:

Do hobbits age at the same speed as humans or slower?

And here:

How did Gerontius Took get to be so old?

Coming of age depends on jurisdiction, rather than some biological fact. Historically there were countries and times when people would come of age at 24 years old, at first period, after succeeding in a ritual quest, etc. Another thing is that the "corresponding" ages of hobbits and humans don't have to be proportional. Probably the best way to determine the average life expectancy of a hobbit is to take all the hobbits whose years of birth and death Tolkien listed, and count their average lifespan. (This might be skewed if in the Shire there is such a thing as lower classes living shorter, but I'm not sure how to take it into account.)