The default vehicle lifetime field sets the amount of hours the vehicle (or system) is in use. This field is not directly used in the FMEDA calculation; however, in conjunction with the on time (t_on), this sets the total Power On Hours (POH) which is directly used in the calculation of the raw (base) FIT rate of the device. The user may alter this assumptions to meet their specific use case. The longer the vehicle lifetime, a larger number of Power On Hours (POH) is used in the calculation thus resulting in a larger raw (base) FIT rate. Please note that for many automotive and industrial devices, this increase in raw (base) FIT rate will be too small to be observable in the 'Totals' tabs.