an apparatus and method for detecting a defective array of nvram cells . a counter is provided which times an erase time interval for the nvram cells during a regular erase function . the computed erase interval is compared with a maximum erase interval to determine at least a first characteristic which indicates the block of nvrams is at the end of its useful life . a second characteristic is determined by computing the slope in the erase time function versus the number of simulated erase functions . when the slope of the erase function exceeds a maximum slope , the nvram array is determined to be at the end of its useful life .