When it comes to using something like a flash drive or external hard drive, you will need to manually plug them in, at the appropriate time, so that the backup can be carried. This may be once a week or once a month, ideally, you want to have as many backups as possible, but you don’t want to overdo it.
Of course, there’s nothing stopping the flash drive or external hard drive from failing. However, with cloud storage this is minimised. You can use the cloud to backup literally everything, and it works considerably faster than other backup methods. Thinking about backing up your tablet or your phone, then cloud storage is something you may want to consider investing in.