That's the only way, unless you can set up some sort of external program to automatically copy them to another drive. A quick Google search turned up a number of free or inexpensive utilities that will automate this for you.
The likelihood of a hard drive going "poof-crash-just-like-that" is pretty low, so manually backing up those files/folders daily shouldn't be too big of a task. You could even save a Windows search (I'm assuming you're using Windows, but I'm sure Mac has similar capability) to find all your PRPROJ files on one or more drives, and then quickly copy them to another location. A little bit manual, but free.
For the Saving of PRPROJ files to another location, I'd incorporate a manual Save_As_a_Copy, into my workflow (I do that often now), directing this to another HDD.
You have 4 Save options: AutoSave (automatic, as the name implies), Save, Save_As and Save_As_a_Copy. This ARTICLE will tell you more about each, so you can decide which works best for you, with any particular need/requirement. As I edit, I use each for particular requirements.
After every session i use the Save a Copy to another drive.
If there is a flaw somewhere auto save will save this.
Auto Save also overwrites itselve which means older versions of the project are lost.
If you Save a Copy each time and dont overwrite you will have an older version of the project.
The damage wont be that great.
The short answer here is that we have no control over where Autosaved files get saved. They go in the same folder as the project file itself.