The answer to this question in my opinion is no. In this blog post I will explain why using an example.
Firstly I have created a new test duration field on my test Project Server 2013 environment, this is called _duration.
For the purpose of this post, I also have a new Project Detail Page (PDP) that only displays the _duration field. A new project is created, the schedule it not important here, just the value you specify in the _duration field. As you can see below, I have entered 10 days:
Save and publish this to Project Server and take a look at the project in PWA. You can see the project in PWA as shown below:
Project Center:
Notice the _duration field correctly shows the 10 days.
PDP:
Notice the _duration field correctly shows the 10 days.
All ok at this point. Before we move on, I just want to show the project options for this project, specifically the hours per day:
Notice this is set to the default 8 hours per day. Update this to 7 hours per day. You will then notice that the _duration field correctly updates to 11.43 days:
Reset this back to 10 days then save and publish the project again.
The Project Center still display 10 days in the _duration field:
The PDP will show the incorrect duration in the _duration field:
The PDP’s assume the default 8 hours per day is used for each project. At this point the PM will probably think, lets correct the 8.75 days to 10 days. So lets do this, this is now correct in the PDP:
Great. Not quite, now take a look in the Project Center:
Notice the 11.43 days. Also check the Project Information in Project:
I was aware of this issue in Project Server 2010 but only just came across the same thing in Project Server 2013.
Hopefully that explains why I answered “no” to displaying duration fields on the Project Server PDP’s, it will save a lot of confusion with your Project Managers! As with all answers there is normally an exception to the rule and you can probably guess what that is. Displaying duration fields on PDP’s will be fine if your projects are 8 hour days 
