Methods of Cloning/Backing Up Internal Drive to 2nd Internal Drive in Enclosure

First, sorry for the terrible title. I couldn't think of a better one.

Here's my deal. I want to buy an internal laptop drive the same size as the one I have now to keep in an enclosure as a backup in case my drive fails (I cannot go one day without a working laptop, thus the need for a drive I can replace).

First, there is cloning. I can clone my drive to that one, but it seems this is difficult to maintain (need to create new clone each time, etc.), and difficult to schedule on a regular basis. I am also not all that familiar with cloning software (suggestions?).

Next, there is the image method, which I already do. This seems as though it would create an issue with loading the image onto the new drive. Is there a way for me to store the images on this drive, and in the need, swap it into my laptop, run a bootdisk, and expand the images onto the drive? It seems I'd need a separate drive to store the image on (which I have, but defeats the point).

The reason I ask is I'm paranoid, essentially. My current and only backup drive is a Western Digital 640 GB "My Book," which I already had to replace once after two months (and the second one is a bit noisier than it was initially). I know it is rare, but in the event my internal drive and the external drive fail, I would want the third (internal in enclosure) drive to stick in my laptop.

Is a clone really the only way to do this? Or is there a way I can do it with the images on the disk itself?

Thank you for your help. Also, I'd like some cloning software recommendations if that's the method you suggest.