Note this only applies to fee based price plans also. To set durations this way click to edit a fee based price plan like so:

You would then click the Category Specific Costs link on the next page as shown:

You'll would then navigate to the category you wish to add these choices to and click to add (to add new category specific pricing) or click to edit (a current category specific price plan) next the category you wish to affect. Once done you'll see the same choices you see in the price plan wide settings above.

Here is a video that explains where to get to all the "duration choice" admin tools: