As a matter of fact, at least here in Germany a lot of cathedrals took decades, some even centuries to build - the Cologne Cathedral, for example, took way over six hundred years. Additionally, they were often built in "batches" and expanded and modified, schedule pretty much depending on some emperor or volunteer donations providing enough funds for the next section.

Me and my s/o, who actually studied a lot of the German cathedrals for her master's degree, went on a tour across a lot of the cathedrals this summer with the 9-euro flat train ticket... it's utterly amazing what medieval people could pull off. If you're interested in old buildings, wait until the successor of the 9-euro ticket comes next summer and go on a trip yourself, it's definitely worth it.