The nursing timer on fast speed starts at 123 minutes, but 'counts' in 3-minute increments and often takes up to 10 minutes longer once zero is reached. We haven't seen issues with the operation of that timer, as long as the computer's system clock is stable, there is no time-travel, and you haven't ever used certain powers on the nursing mom (which you said you haven't). The only way to know for sure in your case is to actually time the nursing process.