Windows 7: Backup of system image?

I perform an incremental back-up every day using the built-in backup program.

How often would you do a whole system image? I was thinking of only doing that every few months or less. Each image would be 80GB.

Unless you make a lot of changes, backup once in 15 days.

I usually only perform a full system image right after installation of the OS, drivers and after I have activated the OS. I then just back up the data.

In the event that something terrible happens, I just restore my image, reload the apps that I actually need (when I need them) and just restore my data.

I do the same thing.

I perform 2 full system images once a month on 2 seperate harddisks. It's about 150 Gb. (tripleboot XP, Vista en Windows 7 Ultimate).

Each time when I make an important change (Windows updates, new programs installs....etc.....etc) I write it down in a word document. So when an important change causes malfunction of my system and when System Restore solves nothing I know exactly what to change after restoring an image.

In between I backup my important files and folders manualy.

Makes sense; I wish I had done that after installing the RTM. I'll do it as soon as my new external hard drive arrives.