Every edit you make (during the learning phase or after it) has some effect on delivery, but not every edit causes the ad set to reenter the learning phase. Only a significant edit causes an ad set to reenter the learning phase. The following are considered significant edits:

• Any change to targeting
• Any change to ad creative
• Any change to optimization event
• Adding a new ad to your ad set
• Pausing your ad set for 7 days or longer (the ad set reenters the learning phase once you unpause the ad set)
• Changing bid strategy
  
  Note: When using campaign budget optimization, switching your campaign bid strategy might cause multiple ad sets within the campaign to reenter the learning phase.

A change to any of the following areas may or may not be significant, depending on the magnitude of the change:

• Ad set spending limit amount
• Bid control, cost control or ROAS control amount
• Budget amount (unless you’re using the target cost bid strategy, in which case budget changes aren’t considered significant edits)
  
  Note: When using campaign budget optimization, adjusting your campaign budget might cause multiple ad sets within the campaign to reenter the learning phase.

For example, if you increase your budget from $100 to $101, that isn’t likely to cause one or more ad sets to reenter the learning phase. However, if you change your budget from $100 to $1000, one or more ad sets may reenter the learning phase.

Common Questions About Campaign Budget Optimization and Learning Phase:

• How long does the initial „learning“ process typically take for ad sets with campaign budget optimization? It’ll take the same time as ad set budgets.
• Will campaign budget optimization cause ad sets to reenter the learning phase as it distributes budget? No, ad sets within the campaign won’t reenter the learning phase as budget is distributed.
• Will making a significant edit to one ad set (meaning the edit is made at the ad set level) cause other ad sets within the same campaign to reenter the learning phase? No, as long as the edit is made at the ad set level, other ad sets within the same campaign won’t reenter the learning phase.
• Will adding a new ad set to the campaign cause the rest of the ad sets to reenter the learning phase? No, adding an ad set to a campaign with campaign budget optimization won’t cause other ad sets within the same campaign to reenter the learning phase.