Our UI allows you to specify your Ad Groups’ relative importance through weighting and then determine how long or how often to show each individual Ad Group, which we call escalation. The escalation feature allows you to sequence your campaign messaging with a more compelling message to a User if they have not converted within a certain timeframe. We recommend escalate after a predetermined amount of days (not impressions)
One Campaign with Two Ad Groups:
Assuming you will be escalating traffic between the 2 Ad Groups, you can escalate the Ad Groups by 'days' or 'impressions'. We recommend that you escalate by 'days' for optimal results. IE, You can serve a set of ads to a User for 7 days with "10% Off" messaging. If the User has not converted yet, on day 8, the User will see the second set of Ads from Ad Group 2 with "25% off + Free Shipping" messaging. The idea is to entice the User with an offer they can't refuse in order to win the conversion.
SteelHouse Pro Tip:
Assign escalation by Days. Additionally, your final Ad Group must be set to 'No Limit' -- this way your second Ad Group will serve for the remainder of the Campaign. If you were to specify a number of Days in lieu of 'No Limit', the Ads from this campaign would stop serving to users before the actual campaign end date. Use the escalation feature to put a new set of ads in rotation to keep the messaging fresh if the user has not converted after a specified period of time.