Can a system image be too old?

I was discussing backup processes with a colleague and he mentioned that he had recently attempted a Win 7 system image install and encountered a warning indicating that the image was more than 60days old and a successful restoration was not likely. This seems a bit odd to me as I understood that one of the advantages of a system image was that you could create one immediately following a fresh OS install and could use it instead of an OS reinstall at some time in the future. Can anyone shed any light on this?