> I keep telling people to make backups of "cloud" services

The usual rule when making backups is that you need 3 copies, one of them offsite. A cloud storage service counts as an offsite copy, but you still need two more, typically one on your computer and one in cold storage (ex: external hard drive).

Treat cloud storage like you treat your hard drive, it can fail at any time. The failure modes are different: mechanical failure vs losing access to your account, but the end result is the same: the system is unreliable and you have to engineer around it.