Interesting link, but not what I was asking about.
In things like Photoshop, you want to save things as a .psd file so that you don't lose layers and what-not.
I assume Inkscape has a similar concept?
When I did my sprite in January, I saved things as a .svg, and as far as I can see, it collapsed all of my work into a static image.
For example, I created a 3 star sprite, and I want to be able to go back into whatever file and move those stars, resize them, change the page size, etc.
I don't think I can go back after saving as a .svg - then again I could be wrong.