Musar zu Bereschit 24:1

ואברהם זקן בא בימים . The emphasis on the word בימים, which at first glance seems superfluous, teaches us that a person must be concerned every single day of his life to do good and not to sin. When he thinks in this vein only, every single day of his life will assume meaning. His reverence for G–d will result in his being granted more years. The years of the wicked, on the other hand, become shortened; this means that even if they live chronologically speaking for many years, the sum total of their life is short, seeing it was not filled with worthwhile activities. When Abraham is described as "aging," this means that he had made every one of his days count.

Nachmanides deals with the problem at length and is worth reading (cf. 24,1). I shall also make a contribution to these puzzling and conflicting statements. Nachmanides follows his method, whereas I shall follow mine.

The verse states, “And Avraham was old, advanced in days [years]” (Bereishis 24:1). This is interpreted in Midrash Rabbah (Parashas Chayyei Sarah 59:6) by Rabbi Abba: “There are people who are ‘old’ but not ‘with days’ and there are others who are ‘with days’ but not ‘old.’ But in Avraham’s case his old age corresponded with his days and his days with his old age.”