Update in place and keep the URL for the vast majority of refreshes, and republish as a new URL only when the topic or intent fundamentally changes into a genuinely different page. The default is strongly toward in-place, because the existing URL already carries the page’s history, its inbound links, and whatever ranking standing it has earned. Throwing that away to “signal freshness” with a new URL is a tactic that costs you equity for no gain, and it is not how freshness works.
In-place updates preserve everything the page has accumulated. When you revise the content under the same address, the links pointing at it still point at it, the search engine keeps the page’s track record, and any improvement you make is read against an established baseline rather than from zero. A page that has been live and linked for two years is a stronger starting position than a brand-new URL, so the sensible move when you are evolving an existing answer is to leave the address alone and make the page better where it already lives.
The exception is real but narrow. If the page’s subject or the searcher intent behind it shifts so completely that you are no longer updating the old page but writing a different one, then a new URL is honest and correct. A post about a discontinued product that you are repurposing into a guide for its replacement is a new page, not a refresh. In that case you create the new URL and 301 redirect the old one to it, so the accumulated equity follows the redirect instead of being stranded.
So the question to settle before you touch anything is whether this is the same page evolved or a genuinely different page. If it is the same answer made current, update in place and keep the URL. If the topic or intent has truly become something else, build the new URL and redirect the old one to it. Default to in-place unless that condition is clearly met.