I agree with what you are saying wholeheartedly - I recommend having more than one backup in more than one location. I personally back up DT using TimeMachine to one set of disks, Carbon Copy Cloner to another set of disks and sync to a total of 3 further devices using Bonjour. In addition, I back up some content using Arq. The backups to TimeMachine and CCC are to disks which I cycle; those not currently active are stored offsite. (What I hope to have considered with this approach is software and hardware failure, timed ransomware and other timed or non-timed destructive malware, loss through carelessness, theft or fire; in addition, because they are both local and the files are stored in non-proprietary format, access to the databases is guaranteed even if DEVONtech were to fail.)