The answer I have isn't an answer to your question about Lemuel Comstock's location around 1840. Maybe the following will be of some interest to you anyway. If you look at message 817 in this forum, and search the online Comstock genealogy book with the expression +Asenath +Davis you will find this:
Family 506 1467. LEMUEL7 COMSTOCK (Israel,6 Daniel,5 Daniel,4 Samuel,3 Samuel,2 William1) born Aug. 13, 1782; died 1856; married Asenath Davis, b. Aug. 14, 1783, of Springfield, N. Y.
Children born in Western, Oneida Co., N. Y., unless otherwise stated (included . . . ) 3221.MARY ANN, b. June 23, 1819; m. Aaron Chase.
It looks like this only confirms what you already know, but the following shows the marriage of Mary Ann Comstock and Aaron L. Chase to have been in Kane, Illinois, rather than in New York.
Aaron CHASESex:M Marriage(s):Spouse:Mary Ann COMSTOCK Marriage:Abt. 1840Of, New York
Aaron L. CHASESex:M Marriage(s):Spouse:Mary Ann COMSTOCK Marriage:12 May 1839, Kane, Illinois