I had my first flock for about 3 years. They'd dramatically slowed down laying, I didn't (or, at least, though I didn't^), have the means to raise replacements, and I was working long hours that made the chickens seem like more of a chore than a joy when I was already tired and sore.
But I knew that I'd want them again when my life changed.
I suspect that the 3-5 year period, when you face the fact that your beloved first hens are now feed-gobbling freeloaders and that raising/integrating replacements is going to be a lot of work, is a common time to decide that you're not going to do chickens anymore.
But for those who pass that first replacement scenario, I think it is likely to last until some significant life change happens.
^If it weren't such a radical idea to raise chicks outdoors I'd have learned that I could have raised the replacements in the carport or on the porch in my mild climate.