Files on my C: drive are fairly static, consisting mainly of just the Windows system files, page file and other programs that I may install or upgrade from time to time. All my work files and TV captures go into different partitions - backups consist of just a simple "copy" to a flash drive for these files.
I will initiate a (Symantec) Ghost backup on the C: drive only after when I have installed/uninstalled new/existing programs or after when there are many changes in the Windows registry due to parameter changes in the Windows system or software program settings that I have made.
This is what I do to speed up my the Ghost backup on my C: drive.