Here’s the list of popes since 1800; dates of rule; date born/date died:
Pius VII March 14, 1800-Aug. 20, 1823. [August 14, 1740 - August 20, 1823]
Leo XII Sept. 28, 1823-Feb. 10, 1829. [August 22, 1760- February 10, 1829]
Pius VIII March 31, 1829-Nov. 30, 1830. [November 20, 1761 - December 1, 1830]
Gregory XVI Feb. 2, 1831-June 1, 1846. [September 18, 1765 – June 1, 1846]
Pius IX June 16, 1846-Feb. 7, 1878. [May 13, 1792 – February 7, 1878]
Leo XIII Feb. 20, 1878-July 20, 1903. [March 2, 1810-July 20, 1903]
Pius X Aug. 4, 1903-Aug. 20, 1914. [June 2, 1835 - 20 August 1914]
Benedict XV Sept. 3, 1914-Jan. 22, 1922. [November 21, 1854 – January 22, 1922]
Pius XI Feb. 6, 1922-Feb. 10, 1939. [May 31, 1857 - February 10, 1939]
Pius XII March 2, 1939-Oct. 9, 1958. [March 2, 1876 – October 9, 1958]
John XXIII Oct. 28, 1958-June 3, 1963. [November 25, 1881–June 3, 1963]
Paul VI June 21, 1963-Aug. 6, 1978. [September 26, 1897 - August 6, 1978]
John Paul I Aug. 26-Sept. 28, 1978. [October 17, 1912 – September 28, 1978]
John Paul II Oct. 16, 1978-April 2, 2005. [May 18, 1920 – April 2, 2005.]
Benedict XVI April 19, 2005-. [April 16, 1927-]
Popes born in 18th century
Pius VII 59; 23 yrs [83]
Leo XII 63; 5 yrs [68]
Pius VIII 67; 1 yr [79]
Gregory XVI 65; 15 yrs [80]
Pius IX 54; 31 yrs [85]
Ave age elected 62
Ave age died 79
Ave length of rule 15
Popes born in 19th century
Leo XIII 67; 25 yrs [93]
Pius X 68; 11 yrs [69]
Benedict XV 59; 7 yrs [67]
Pius XI 64; 17 yrs [81]
Pius XII 63; 18 yrs [82]
John XXIII 76; 4 yrs [81]
Paul VI 65; 15 yrs [80]
Ave age elected 67
Ave age died 79
Ave length of rule 14
Popes born in 20th century
John Paul I 65; 0 yr [65]
John Paul II 58; 26 yrs [84]
Benedict XVI 78;
Ave age elected 67
Popes over 70 years old when elected (since 1700):
Pope Benedict XIII 75; 5 yrs died at 81 (1724)
Pope Clement XII 78; 9 yrs died at 87 (1730)
John XXIII 76; 4 yrs died at 81 (1963)
Benedict XVI 78
There does seem to be something about being voted in as pope that helps your longevity, as popes have consistently outperformed their fellow Italians in the last three centuries. (It may be argued, and indeed has been, that JPI died of unnatural causes, in which case he can be removed from calculations under the acts of God/assassinations sub-clause introdued above.) Getting the job seems to have a positive effect on life expectancy, even for those who get it late, who have all gone on to live into their 80s.
So, no evidence that the cardinals expect Joe to peg out any time soon. A suggestion, though, perhaps, that, as highly intelligent folk well versed in PR, they might want to give the impression of choosing someone conservative while appearing to believe that he will not be around too long to strengthen the grip of the conservatives on the church.