You really need to know more about it than your spec.. Is 25 amps maximum motor current? Motor inductance. For example a motor with a few microhenries will be different than one with millihenries. Then PWM frequency.
that's a SINGLE PULSE rating, not a repetitive rating. that's like saying a speaker has the capability of two feet of cone excursion, ONCE.... use the right tool for the right job. if the diode fails, you will be driving a direct short with the transistor, and it won't last more than a few milliseconds either.
I think the maximum diode current occurs at a 50% duty cycle and high motor inductance. So a 25 amp motor will store 12.5 amps. Since the diode will see the same current during fly-back it will see 12.5 amps but only for 50% of the time or 6.25 amps average. Higher duty cycle will produce diode peak currents up to 25 amps but for only a very short part of the PWM cycle. There may be some reverse recovery time currents but with a schottky diode they can probably be ignored for this discussion.