Running CHKDSK /R is one of the first troubleshooting step you take when you are working on a system that throws file system errors. That is to eliminate the file corruption possibility (or if you confirm it, take proper actions). In a certain way, there's no point in running /f alone. Imagine you run CHKDSK /F, it finds bad sectors with file systems on it, but just mark them as bad and leave the data where it is. You had the possibility to solve system file corruption, but you didn't. Also, if you think that running a CHKDSK /R scan is long, simply do it overtime or during a period where you're not at your computer. This is what I do and recommend to the users when I make them run it and there hasn't been any problem in doing so.