It is always wise to give the back up partition sufficient space, so that back ups can remain on the drive for more than a few days. There have been many posts, indicating that a problem had ocurred and that SR, could not solve the problem because it did not go back far enough.
I realize that there are people out there that do not have that much room to devote for a restoration drive. My advice to them is to make a system image, put it on an external hard drive and update it once a month. In that case, whatever problem you encounter you have the ability to make things right with a current system image. In fact my advice to everyone is to follow the advice on creating a current system image. There is software out there that, in my opinion, surpasses the capability of Windows system image and it is free, Paragon http://www.paragon-software.com/home/db-express/