Archiving Incremental File And Image Backups

I have clients that I am taking offline, but would like to keep the latest backups for an indefinite amount of time. Some of these clients are already offline.

If I set the latest backups to Archived and those are incremental backups, will I have all data back to the current Full backup or only the data represented in those incremental backups? I assume that in time the current full backups will be deleted as server retention policy removes older files.

I imagine the best thing would have been to perform unscheduled full backups on clients just before I removed them.