Generally speaking, most people recommend making a system image on an external hard drive rather than using DVDs. It usually takes multiple DVDs (as you're finding out) and the chances are much greater that a DVD won't burn correctly. If one of those DVDs is corrupt in any way, you won't be able to restore the image.
Creating a system image is not the same as creating a repair disk. A repair disk is for a worst case scenario when you can no longer boot your computer and acess Windows 7. You set your BIOS to boot from the optical drive as the first choice (rather than booting from the hard drive.) You insert the repair disk, let the computer boot from that disk, and then you can access several repair functions including the ability to restore your machine from the system image you made earlier. It's been my experience that the repair disk will easily fit on one CD and it takes about 15-20 minutes to create it.
Many people recommend the free Macrium Reflect
over the Windows 7 imaging tool or paid products.