UWP - in-app products - speed of GetAppLicenseAsync()

I am migrating a

• Windows 8.1 app which used the Windows.ApplicationModel.Store namespace for IAPs to
• Windows 10 UWP with the Windows.Services.Store namespace

For determining the license status of in-app items, the former had a LicenseInformation property whereas the latter has a GetAppLicenseAsync() method.

So, with the former the information about IAPs was (seemed to be?) there instantaneous, whereas with the new method, the information could take longer.

My question: Is the newer concept really slower or is the speed the same and the new async method just reflects the fact that getting the information has never been instantaneous?

My app needs the information about all purchased items already at app start. So, the only way I see is that I call GetAppLicenseAsync() at app start and wait until the information is there before I show the user interface.

Edit 2017-07-25:

My question in short is: Is there a time of how long the GetAppLicenseAsync() method will take at most?