How long did Romans expect to live?

[Caballo]

How long could a Roman expect to live?

And is there an issue between life expectancy and life span? We have some examples from Roman gravestones of some very long lived people-but infant mortality could skew the stats.

"Life expectancy is often confused with life span to the point that they are nearly synonyms; when people hear 'life expectancy was 35 years' they often interpret this as meaning that people of that time or place had short life spans. One such example can be seen in the In Search of... episode "The Man Who Would Not Die" (About Count of St. Germain) where it is stated "Evidence recently discovered in the British Museum indicates that St. Germain may have well been the long lost third son of Rákóczi born in Transylvania in 1694. If he died in Germany in 1784, he lived 90 years. The average life expectancy in the 18th century was 35 years. Fifty was a ripe old age. Ninety... was forever."
This ignores the fact that the life expectancy generally quoted is the at birth number which is an average that includes all the babies that die before their first year of life as well as people that die from disease and war. In fact, there are examples of people living far beyond the life expectancy of their time such as Democritus, Socrates, Roman emperor Augustus, Saint Anthony, Michelangelo, and Ben Franklin.
It can be argued that it is better to compare life expectancies of the period after adulthood to get a better handle on life span. Even during childhood life expectancy can take a huge jump as seen in the Roman Life Expectancy table at the University of Texas where at birth the life expectancy was 25 but at the age of 5 it jumped to 48. "

Here is that table from the University of Texas:-

Life Table

Life Table Approximating Roman Population (simplified from Coale-Demeny 2, Model South, Level 3, Female as cited in Parkin, Demography and Roman Society)
x e(x) x+e(x) C(x)
0 25 25 3.3
1 33 34 9.3
5 43 48 9.8
10 41 51 9.3
15 37 52 8.9
20 34 54 8.3
25 32 57 7.8
30 29 59 7.2
35 26 61 6.6
40 23 63 6.1
45 20 65 5.6
50 17 67 5.0
55 14 69 4.4
60 10 70 3.5
65 8 73 2.5
70 6 76 2.2
x = Age
e(x) = Life Expectancy at age x
C(x) = Percentage of population between this age and the next
Infant Mortality rate = 319/1000
Stationary population requires GRR = 2.543 (i.e. about 5 children per mother, live-born)

NB: All the figures below are approximations based on comparative evidence, rather than on the (largely inadequate) ancient statistical data. Among other potential problems:
(1) Several scholars would hold that the average life expectancy at birth assumed below (25 years) is too optimistic, at least for most ancient populations (NB: keep in mind that life-expectancy-at-birth is a mean, not a median; high infant mortality conceals the susbstantial number of people who will live well past this age.)
(2) These broad estimates do not allow us to account for possible variation across areas, socio-economic classes, or sex.
For more information see (among other things):
Roger Bagnall and Bruce Frier, The Demography of Roman Egypt (Cambridge, UK 1994).
Tim Parkin, Roman Demography and Society (Baltimore 1992).
Richard Saller, Patriarchy, Property and Death in the Roman Family (Cambridge, UK 1994).

Plus there are some gravestones indicating an advanced age for some soldiers (but they could be the exception...)

And in the 1st century BCE War Scroll from the Dead Sea Scrolls, they write this. "The men of the army shall be from 40 to 50 years old. The inspectors of the camp shall be from 50 to 60 years old. The despoilers of the slain, the plunderers of booty, the cleansers of the land, the keepers of the baggage and those that furnish the provisions shall be from 25 to 30 years old." (Complete Dead Sea Scrolls, Penguin)