The hydrothermal stability in the form of the shrinkage temperature (Ts) is a fine measure of the deterioration of vegetable tanned leathers. Previously, it has been demonstrated that the Ts can be predicted by multiple regression modelling based on parameters for the chemical breakdown of the collagen and tannin structures, the sulphate content and acidity of the leather as well as the interaction of these four parameters. In the present paper, several deterioration profiles are suggested for both the natural and artificial aged leathers based on significant regression analyses of the grouped data. The possible existence of several deterioration profiles is supported by more than 100 years of observational and experimental studies of natural and artificial ageing, and is probably mainly due to difference in tannin type and storage conditions. On this basis the problems in using simple standard artificial ageing systems are discussed, and improvement of more complex systems suggested. The latter based on continuation of combined observational and experimental studies using the multiple regression modelling of the Ts as an instrument for adjusting and developing the ageing system.