A catalyst experiences numerous physico-chemical changes during its life. Often these changes are a priori regarded as 'unwanted' in terms of catalytic performance. However, understanding the details of these transformations offers the opportunity to control them. By distinguishing which changes do contribute to deteriorate the catalytic performance, vs. those that bring improved catalytic behaviours, it becomes possible to channel the system towards specific modifications. Along this strategy, a priori unwanted modifications of the catalysts become beneficial when induced and exploited in suitable conditions. This paper revisits examples wherein such an approach was payful: (i) MoO3 + alpha-Sb2O4 mixtures and (ii) Re-Sb-O compounds, explored in the oxidation of isobutene to methacrolein, (iii) gamma-MnO2 explored in the total oxidation of methanethiol, and (iv) (NH4)(6)P2Mo18O62 polyoxometalate explored in the oxidative dehydrogenation of 2-butanol to methyl-ethyl-ketone. (C) 2013 Elsevier B.V. All rights reserved.