We monitor the mechanical strain evolution with typical use in the quantum well of AlGaAs/GaAs-based high-power diode laser arrays (cm bars) by spectroscopic means. We show experimentally that pristine devices are essentially uniaxially compressed along the 110-direction with a strain maximum of -0.16% at the center of the device. At the device edges, almost no packaging-induced strain is detectable. After 500 h of continuous wave operation at a current of I=80 A, the strain is reduced by 50%. Furthermore, we observe the growth of a localized region of compressive strain, of hydrostatic symmetry, in one emitter of a particular cm-bar. A compression of about -0.017% is observed, and is most likely caused by point defect accumulation. Our results demonstrate information about absolute strain values and, at least in part, about strain symmetry as well can be obtained by spectroscopic means even within packaged complex optoelectronic devices.