22 hours per week, the U.S. Average.
Your mileage may vary. ;-)
Given your assumptions my numbers are in close agreement with yours. I get about 3.8 years.
Given the low end 25,000 hour estimated life, it would last about 22 years.
That would save you about $260 in energy costs assuming the current rates don’t go up.
Given Chinese manufacturing quality? You’d about break even...