in his blog, RevK talks about Pi bakery http://www.revk.uk/2018/01/tweaking-raspberry-pi-install-image.html
Interesting link.
My very simple approach with the 3 RPi's I look after is to make periodic disk images on my desktop Windows PC using "Win 32 Disk Imager" just remove the SD cards and directly insert into PC SD slot, images being stored on my NAS drive.
DSLStats program revisions usually dictate the backup frequency, also carry out Raspbian system updates at the same time.
Probably more elegant backup solutions available but this works for me and requires minimal effort on my part.
Realistically, hard drives and certainly SSD's can & do fail in service, all be it at a statistically much lower frequency than SD cards, having a backup is just a basic good housekeeping requirement with any system.