Going broad pays off once you have won your focused area, established real topical authority there, and have the trust and capacity to extend into adjacent topics that build on it. Before that point, broadening just dilutes a weak base. The turn comes when focus is genuinely won, not when you are merely tired of the narrow lane, so the rule is win the focus first, then extend into adjacent topics. Breadth is a reward you earn, not a strategy you open with.
The signal that the turn has arrived is concrete. You can see that your focused area actually ranks and is recognized, that the search engine treats your site as a credible source on it, and that you have the resources to take on more without starving the core. When those hold, expansion into nearby topics rides on the authority you have built: the new pages inherit trust from a site already proven in a related space, so they have a real chance rather than starting from zero.
The instinct to broaden early, to capture more before you have captured anything, is what to resist. Adding topics to a base that has not yet won spreads your authority thinner across more ground, and a thin base supporting a wide footprint ranks for little anywhere. The extension also has to be adjacent, topics that build on what you have won, because authority transfers along related ground and not into unconnected subjects. Broadening into the unrelated forfeits the advantage your focus earned.
For your next expansion decision, check the foundation before you widen. Ask whether your focused area is genuinely won, ranking and recognized, and whether the topics you want to add actually build on it. If both are true, extend into those adjacent areas and let your earned authority carry them. If the focus is not yet won, hold and finish winning it first, because breadth pays off only as a reward for focus, never as a substitute for it.