A comment that I heard somewhere resonated with me: Don't retire FROM something; rather, retire TO something.
I think we should all have plans to stay active with friends, in the community, etc. ... those plans could involve part-time or seasonal work, but they don't have to include paid employment. Volunteering, hobbies, social activities, or any combination ... those things can fill your time /prevent boredom just as easily as a job ... but without the everyday commitment of a job.