I would give a page at least three to four months after the last real change before judging it, but check a few things earlier than that. First, is it even indexed and is Google showing the version you expect. Second, look at the queries in Search Console. If impressions are rising but clicks are flat, the page is ranking and the title or snippet is the problem, not the strategy. If impressions are flat, compare it against the pages ranking above you and see what they cover that you skip. Only change direction when you have a clear reason, like the intent being wrong, not just because a few weeks passed with no movement.
