I backup up my work-in-progress material every sunday (just finished in fact).
I'm currently using two 2.5" USB3 enclosures with a WD Black disc and a SSD for faster (smaller) backups. I'm very fortunate to have never lost any important data, but I'm very aware that it could happen at any time - hence the weekly backup. I also image the OS discs (I use 2 PCs) every week too.
Pretty dull stuff, but pretty critical nonetheless.