I think into the 1900s. I think those Sears houses were sold into the 40's, maybe 50's?
I lied, the last year was 1940
I lived in one, a four square from sears built in 1910
I have a Sears Roebuck catalog from the late 19th century and it doesn't have any tiny houses.
My grandparents bought their house from Sears back then. I can vouch for this!