What triggers it
A bid strategy enters a Learning status in four documented cases: the strategy was recently created or reactivated; a setting for the strategy was changed; campaigns, ad groups or keywords were added to or removed from it; or, on Shopping campaigns, certain ad group target changes. Notably, changing a campaign's budget is not among Google's listed triggers, despite being the change advertisers most often avoid for fear of "resetting learning".
How long it lasts
Google says calibration typically takes 1 to 2 conversion cycles, and can be faster with more conversion data. That makes it far more painful in B2B than in high-volume ecommerce: low conversion counts and long sales cycles both stretch the window. The practical response is to batch significant changes together rather than spread them across a week, which is Google's own Smart Bidding guidance. We break down the full trigger list in what actually puts a Google Ads campaign into learning. Switching a campaign onto a Smart Bidding strategy such as Maximize conversions, including from Maximize clicks, counts as a new bid strategy, so it starts this window. Meta has its own, different learning phase driven by event volume rather than by specific edits: see learning limited.
Common questions
Does changing the budget reset the learning period?
Google's learning-period documentation does not list budget changes as a trigger. Budget can still affect performance, but through what the campaign is able to buy, not by restarting learning.
How long does the Google Ads learning period last?
Typically 1 to 2 conversion cycles, per Google, and faster when there is more conversion data. Low volume and long sales cycles extend it.