Allow 1-2 hours to explore the abbey complex and the accessible church areas; more if climbing Lange Jan tower.
A visit to the 'Old Middelburg Cathedral' (referring to the accessible parts of the Middelburg Abbey and Nieuwe Kerk) typically takes between 1 to 2 hours. This timeframe allows for a leisurely walk through the abbey courtyard, explorations of the publicly accessible sections of the Nieuwe Kerk and Koorkerk, and time for appreciating the exterior architecture.
If you plan to climb the Lange Jan tower, which offers commanding views of Middelburg and the surrounding Zeeuwse landscape, allocate an additional 30-60 minutes for the ascent, descent, and time spent at the top. The climb involves many steps, so factor in your physical condition. If you are a history enthusiast who enjoys reading information panels or participating in guided tours (if available), your visit might extend further.