A variety of polymer parts used in microsystems technology is produced by injection molding. For dimensioning and design of these products, both the material properties and changes during the life cycle have to be taken into account. The aging behavior of parts with decreasing dimensions or of parts processed under different cooling conditions is discussed in terms of their morphological and mechanical long-term properties. The results indicate that a decreasing part size leads to higher post-crystallization and higher thermo-oxidative degradation. This leads to size-dependent changes in mechanical properties. Adjusted process conditions by application of thermal low-conductive mold materials can favor the process-related properties and thus the long term properties can be improved.