When you give a code section a name, it is essentially for giving it a name. This can be for any of several reasons, but the crucial point is if you can give it a meaningful name which adds to your program. Names like "addOneToCounter" would not add anything, but
If you need a rule for finding out if the snippet is too short or too long, then consider how long time it takes you to find a meaningful name for the snippet. If you cannot within a reasonable amount of time, then the snippet is not a suitable size.