Sforno on Exodus 7:7/ספורנו על שמות ז׳:ז׳

1ומשה בן שמונים שנה, even though he was an aged man both he and his brother rose early in the morning to do their Creator’s bidding. Although some people lived to a ripe old age in those days, eighty was an age which was considered as very much part of what we call “old age.” We know from David in Psalms 90,10 that reaching the age of 80 was considered an exceptional feat, i.e. kindness of G’d.