A lighting unit is described which has a discharge lamp (1), in particular a high pressure or high intensity discharge (HID) lamp or an ultra high performance (UHP) lamp, a lamp driver (2) and a cooling device (3). To reduce mechanical stresses caused by temperature variations in the lamp (1), one or more operating parameters of the lamp (1) are detected. In addition, a control unit is provided for controlling the lamp driver (2) and/or the cooling device (3) at least during switching on and/or off of the lighting unit in such a way that there is no excursion from a predetermined range of the at least one operating parameter. By selecting the parameter range suitably, the service life of the lamp may be extended considerably or the power of the lamp may be increased while the service life remains the same.