The influence of rest periods on the lifetime of lithium-ion cells is investigated. The investigations focus on commercially available cells (type 18650) with a lithium–nickel–manganese–cobalt-dioxide (NMC)/lithium–cobalt-dioxide (LCO) blend and lithium–iron–phosphate (LFP) as cathode material and graphite as anode material. The above test cells are subjected to different cycle tests. Important influence factors in addition to the relaxation time are: the current, the temperature and the state of charge (SOC). We were able to detect an increase of capacity (e.g. 0.1% of the nominal cell capacity for LFP test cells) after a rest period of 120 min in our measurements, the so called relaxation effect. Further, the question is answered, whether relaxation affects battery lifetime. This was achieved by cycling cells with and without different rest periods at different temperatures and C-rates with a total of 50 test cells. However, no observable differences between cells with and without rest periods (≤2 h) were found. Moreover, experiments with many small breaks or one larger break showed that the duration of one continuous relaxation time is more important for the aging behavior, than the sum of rest periods. In addition, also impedance spectra were evaluated.