MTBF
Mean Time Before Failures (MTBF) calculates the average time between failures of a system/equipment. It is an index that shows a repairable mechanical or electronic system’s/equipment’s stability and reliability when in normal operation. It is generally used to calculate when equipment may fail unexpectedly in the future. A product is more stable and reliable when its number of MTBF is higher (usually measured in hours).
 
Lifetime
The lifetime here may also indicate the lifespan of an electrolytic capacitor as the lifetime of a power supply is usually determined by the electrolytic capacitor. The lifespan of an electrolytic capacitor is a reference value that is calculated according to serial factors including the rising temperature of the electrolytic capacitor. In general, 10℃ of temperature decreasing of the electrolytic capacitor will double the lifetime of the power supply.