Currently, up to 6 months of data is kept in table CE_SCANNER_CONTEXT.
This 6 months purge actually applies to all data related to historical background tasks.
Given that CE_SCANNER_CONTEXT stores scanner context as file data, the size of this table can grow quite big on disk depending on how many projects are processed, how frequently they are processed and how big the projects are.
Given that scanner context is only used for diagnosis (ie. they are seldom used when everything goes right), it may be appropriate to drop this information sooner than 6 months or according to another criteria (eg. keep only the XX most recent contexts for a given project).