With regard to lifetime prediction of technical textiles, the correlation of relaxation master curves (RMC) constructed from short-time relaxation measurements performed under variation of (a) elongation and (b) temperature with real-time behavior of PET fibers was studied. The comparison with relaxation measurements covering several days indicated that the actual behavior of the material was better described on the basis of the 'time-temperature-analogy'. Analyses of hydrolyzed material showed that the reliable construction of the RMC of aged monofils was possible by means of a 'time-aging parameter-analogy'. The obtained RMC exhibited a congruent shape to the RMC of the new material, but was shifted on the logarithmic time axis. It is concluded that this time-shift relates to the aging acceleration effected by the hydrolyzing procedure. The similarity of the shape of the curves also indicates, that the RMC of the new material gives a satisfactory prediction of the actual aging behavior.