As long as the structure of the new files Hasn't changed and the names of the fields are the same. there shouldnt be any problem. you can go one step further and concatenate your new data to the old and keep both!.
If you are taking about qlik sense desktop then you have to open the app and go into the Data Load Editor and click the Load Data button. Providing the folder connection path is pointing to the same location where the file is located, they would not need to change this.
In the Qlik Sense full platform (server) and Qlik Sense Cloud Business, data refresh are done on a scheduled basis or as needed.