Rebuilt 1986-88. That is the only date that matters...actual vs. projected service life past overhaul. The 01500/01600's are mechanically younger than the never-rebuilt Orange Line cars. They're past end of life, but 1960's frames aren't the reason...late-1980's parts that've used up their rated duty cycles are. And rebuilt in the last 5 years. The 01700's are not at end of life or past rebuild age. Their rebuilds are good for 10 years with the early cars from the rebuild program slated for retirement right at the end of those 10 years. Right now they are the BEST condition of the fleet. They could have been rebuilt for >10 year life extension, but parts are getting scarce for DC traction vehicles so it was better to go minimal.
With a 25-year rated initial lifespan. This year, 2019, is year 24-25. They're not EOL yet, and will only be 2 years over at retirement (not a problem).
There a ton of problems with insufficient RL investment writ-large, but this 50years!50years!50years! meme is hysterical distortion. The 015/016's are in deplorable condition...because riding a rebuild 32 years is enough of a travesty. But trains do not have model years like cars, so the year the aluminum shell was pressed does not dictate years of roadworthiness.
In terms of actually getting the public to support action, pedantry drools while snappy talking points rule.