Usually it is the data that dictates how long the project takes - how much there is and how difficult it is to get at.
Over a simple data set which is simple to access (a basic spreadsheet for example) you can create something useful in just a couple of hours. If you need to connect to an API and build a data extraction routine over that it can take a few days to just get at your data.
The great thing about Qlik Sense is that you can evolve your applications, starting with the basics and they layering on extra data and visualisations as you go.
A couple of days will usually yield something that users can start getting real benefit from. How long you spend growing that and doing more with it depends on how much time you want to spend on it. Ten days would allow someone to deliver on large data with complex requirements.
