Product configurators have been important enablers of customised product design. In a configuration process, customers need to specify the attribute choices that best satisfy their needs. A combination of customer decisions then informs the desired product. Psychology and information retrieval researchers have acknowledged that time is an important factor in measuring customer satisfaction with decision-making process. Some recent studies have also shown that the subjective perception of time is an even more relevant measure of customer satisfaction. However, it remains unclear what factors are most significant in affecting a person's subjective perception of time. This study investigates the relationship between people's experience with the on-line configuration process and their subjective perceptions of the time involved. Empirical experiments are designed to answer the relevant research questions. The experiment's results show that two factors, namely the difficulty of the task and the customers' motivation to process information, both significantly affect customers' perceptions of time. We also find that customers' perceptions of time are significantly correlated with their satisfaction with the configured products, and that perceived time is moderately correlated with satisfaction with the configuration process.