It appears Mary's birth and death dates were taken from a tombstone and that Mary was lying about her age because Mary, d/o James & Catharine HEETER, was born in 1844/5.  Either that, or our subject has been attached to the wrong parents.

1.  Marriage Record:

2a.  1880 United States Census and National Index (LDS Family History Resource File: CD-ROM Library):¤•

Census Place: Cass, Huntingdon, Pennsylvania
Source: FHL Film 1255134; NARA Film T9-1134; Pg 249A
	Relation	Sex	Marr	Race	Age	Birthplace	Occupation	Fa	Mo
Scot W. CORBON	Self	M	M	W	31	PA	Farmer	PA	PA
M. F. CORBON	Wife	F	M	W	30	PA		PA	PA
Charls W. CORBON	Son	M	S	W	8	PA		PA	PA
James E. CORBON	Son	M	S	W	7	PA		PA	PA
Estela B. CORBON	Dau	F	S	W	5	PA		PA	PA
Ira R. CORBON	Son	M	S	W	3	PA		PA	PA
Anna M. CORBON	Dau	F	S	W	1	PA		PA	PA
Lewis CORBON	Father	M		W	70	PA	Boarder	MD	MD

Mary's middle initial is I, not F (see next source).  If Mary's age in the 1860 census is correct (see her parents' page), then she is here fibbing about her age (she should be 34).  And if Mary was older than Winfield, she would certainly have lied about her age when he was courting her, most likely carrying that lie to her grave.

2b.  1880 Census Images (online at Ancestry.com; Image #5 of 37):  Cass Twp., Huntingdon Co., PA, p. 249A, PN 5, SD 7, ED 189, 42/49, enumerated 5 Jun 1880, official enumeration date 1 Jun 1880.  I checked the page image, and Mary's middle initial is definitely I, not (remotely) F.  Listed two households from Elijah CHILCOAT; and, in the other direction, nine households from Amon GREENLAND, who is living with Moses GREENLAND.