I have only second hand info but, if you're talking about retiring from working, as opposed to retiring from operational ATC but continueing to work, a friend of mine summarised it thus: as soon as you change your maths calculations from working out how much money you would "lose" by retiring early, to working out how much money you need to maintain & support the lifestyle you want to live...you'll probably retire the next day! That's what he did, & he hasn't looked back, since.
I'd say early retiring was the best career move my dad ever made...albeit he has health issues one would expect at his age, he's healthier & happier than I ever recall him being when he was working. Dieing in harness is no reward, as far as I'm concerned; I aim to follow his example, for possibly the first time in my life
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