Most practically relevant domains include some degree of conceptual dynamics, i.e. new conceptual elements arise, and some old ones become irrelevant. In the products and services domain, for instance, corporations are continuously inventing new types of goods; and in physics, scientists may discover new types of particles or relations between them. This type of change imposes a substantial challenge on building up-to-date domain ontologies. While most research on ontology evolution has focused on technical solutions for managing such change that has already materialized in the ontology formalization, the order of magnitude of dynamics in real-world domains as the input variable to ontology engineering has not yet been studied. In this paper, we (1) provide a generic simulation model, based on a colored Petri-net, for measuring the conceptual dynamics and the resulting domain coverage of ontologies and (2) quantify the dynamics in three selected areas, i.e. for computer components, pharmaceuticals, and for methods, recipes, and procedures in the inorganic chemical technology sector. We can show that all three areas undergo a substantial conceptual dynamics and that this may lead to weak domain coverage in respective ontologies. Based on these findings, we (3) discuss approaches of how the engineering lag of building domain ontologies can be reduced.