I recently joined a company as an SF/MC admin. We have Sales Cloud and Marketing Cloud and are using Marketing Cloud Connector to sync many objects (20+) over to Marketing Cloud. One of the objects is Individual Email Results - and there are 25M+ of these records being synced from SF to SFMC. I know IERs get synced over to Salesforce from our SFMC sends, but why would you sync this information back every 15 minutes? Is there any value to having that data synced back into a Data Extension? I've never seen this object sync'd before so trying to figure if there is some sort of benefit to having it there before I delete it.
It all depends on the use case. One that is quite common is enriching the IER information. In that case you would synch the IER records to SFMC to include them in SQL queries and then you would update them back in Salesforce with additional information.
And if you’re synching that object already, it doesn’t really matter how often it gets refreshed.
I’d check with the users why they are synching it and what they use the data for.