Titan's atmospheric chemistry modeling is presently limited by the lack of knowledge about many reaction rate coefficients at low temperature (50-200 K). Considering the difficulty of measuring such data, the only way to improve this situation is to identify key reactions as the ones for which better estimations of reaction rates is guaranteed to have a strong influence on the precision of model predictions. This is a slow iterative process, the limit of which has never been clearly defined in terms of model precision. The fact is that this limit is not a fully deterministic simulation, since one should not expect all reaction rate coefficients ever to become available with null uncertainty. The present study considers a quite optimistic scenario, in which all reaction rate coefficients in the chemical model are assumed to be known with a 10% relative uncertainty. The implications for chemical growth modeling are discussed. © 2010 The Royal Society of Chemistry.