Final answer:
The deacon's masterpiece in the poem by Oliver Wendell Holmes, Sr. lasted exactly 100 years before falling apart.
Step-by-step explanation:
The question 'The deacon's masterpiece lasted how many years?' refers to the poem 'The Deacon's Masterpiece or The Wonderful "One-Hoss Shay"' by Oliver Wendell Holmes, Sr. This poem presents a metaphorical narrative of a one-horse shay (a type of buggy) that is so well made that it lasts exactly 100 years to the day before it falls apart all at once. The poem is a reflection on the idea of planned obsolescence and the notion that something can be too well made to be practical. However, none of the provided references directly answer the question about the deacon's masterpiece's duration. The student appears to be asking about a specific literary piece, and the reference to the duration is about a proverbial expression within that work rather than a historical artifact or a restoration process.