Nominally retirement is "forever" in that once you are retired your pension/savings/whatever is funding your existence needs. Having lived most of my life in the SF Bay area I've watched as my cohort came here as college grads, went through the various tech life cycles, and then aged out into "retirement." I put it in quotes because some retired voluntarily, others did not. Involuntary retirement or "funemployement" as the euphemism goes, was typically below the level of flexibility that they had imagined they would have being retired.
Various life events, health issues, marital issues, Etc. spread the spectrum even further. As a result the 'basic income' for this cohort ranges from just below 'covering groceries, utilities, and rent in a low cost of living area' to an annual travel budget, replacement budget for cars/boats/etc, and possibly a second property with some 'feature' (like a ski cabin, a beach bungalow, etc).
What is consistent across the spectrum is a desire to "do something productive with their time." That skews towards volunteer work if their basic life needs are met, piecework if having extra money would meet some currently unmet needs. I don't think I know anyone who could sit in the rocking chair on the patio every day and watch the sun come up and go down, or spend every day at the golf course or some other leisure activity, choose to take that path.
That said, pretty much everyone I know who has retired took an extended amount of time (typically months) to 'unwind.' Once unwound, life seems to assert itself.
Now I don't think this is scientific, its a very specific group of people. Generally professionals who worked in office jobs vs trades. And a number of them 'fail' at retirement which has them going back to work because they didn't have sufficient tools for creating their own direction or something. But laziness isn't a trait I've seen. A completely different direction perhaps, but a direction rather than standing still.