In some instances, a percussion part will only require one instrument. Using a single staff can clean up a part so that the rhythm is very clear and in no way crowded by other details. 
It’s also acceptable to change note heads if the single instrument is being played with more than one sound, such as a snare drum that is sometimes hit not the rim, as seen below.
Using any more than the single line, however, is sloppy and difficult to read, as using multiple sounds around a single line lacks clarity.
Staffs with 2 or 3 lines, in my mind, follow similar rules, meaning that using note heads on the line is fine, but going between or outside is confusing. I feel that 4-line staffs look too similar to the standard 5-line and therefore should never be used.
Adam Holmes 