Didn't find a death, but this would make it after 1920.
Source: "United States Census, 1920," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MN29-657 : accessed 1 December 2016), Thomas M Lilly, Jumping Branch, Summers, West Virginia, United States; citing enumeration district (ED) ED 142, sheet 9B, line 73, family 145, NARA microfilm publication T625 (Washington D.C.: National Archives and Records Administration, 1992), roll 1968; FHL microfilm 1,821,968.
Thomas M Lilly Head M 64 West Virginia
Mandy M Lilly Wife F 53 West Virginia
James M Lilly Son M 28 West Virginia
Cyrus W Lilly Son M 20 West Virginia
Hettie M Lilly Dau F 15 West Virginia