As the 'Grand Velsen Cathedral' does not exist, no duration can be provided for a visit. Typical church visits vary.
Since the 'Grand Velsen Cathedral' is not a recognized attraction, there is no set duration for a visit. For comparison, a visit to a historical church like the Engelmunduskerk in Velsen would typically short, perhaps 30 minutes to an hour, depending on whether there's an ongoing service or special exhibition.
If one were to visit a major cathedral like the Sint Bavo in Haarlem, a tour could last anywhere from 1.5 to 3 hours, allowing time to explore the architecture, stained glass, and any special exhibits. It is important for visitors to clarify which specific religious site they wish to visit.