One possibility for prediction of lifetime of polymer products is given by the estimation of the limits of application by time-temperature-extrapolation of measured damage processes. A time-lapsing method for describing aging is given by the extrapolation with the statement of Arrhenius. If the temperature is not constant over lifetime there are two possibilities to estimate lifetime by time-lapsing lifetime tests. When the maximum temperature is supposed for the whole lifetime, an overdimensioning of the product is the result. The other way is a functional estimation of time-temperature-collectives for a more precise prediction of lifetime, which is shown in this presentation.