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...
I should have said, “About the end of the fourth year in use”, which is exactly 3.793 years by my calculations. We disagree by 23 hours.
:-)