Effect of the duration of annealing at 380 degreesC on the structural state and magnetic properties of the Fe81B13Si4C2 alloy was investigated in some detail. The amorphous ribbons of the alloy were obtained using two technological variants: with an overheating and without overheating of the melt above the critical temperature. The samples of ribbons that were obtained with overheating exhibited higher magnetic properties after an optimum annealing duration. The magnetic properties of alloy samples that were obtained without overheating decrease sharply after holding for 20 min. The results obtained, on the one hand, indicate the presence of the effect of structural heredity and, on the other hand, indicate a way of significant improvement of the time-temperature stability of this alloy and products made of this alloy.