Let's list all cases/situations when the Time Machine can't provide you with a backup of your data. Just to be sure my understanding of TM capabilities and its properties is fine. Only this way the decisions regarding using TM and eventually extending the backup plan with additional solution can be right. I kindly ask you to give a feedback if the summary is correct, or if any situation/case is missing on the list. * The free space of storage used for backups runs out. Well, this is a generic problem of limited storage space resources each backup solution will be affected by. So, it does not seem to be TM specific problem. * As soon as the original file/folder was removed intentionally, or unintentionally by any mistake or other there is no guarantee any more the TM will keep a backup of the item on the backup storage.