parshanut torah comment - Why should the patriarchs have lived to 180?

Rashi to B'reshis 25:30 says that Avraham should have lived to the age of 180 had his life not been cut short.

Yitzchak lived to 180.

The Daas Z'kenim to B'reshis 47:8 quotes a midrash as saying that Yaakov should have lived to 180 had his life not been cut short.

Does anyone explain why they should have lived to 180?

Note that I'm not asking why they should have lived to the same age as one another (although that's an interesting question, too). I'm asking why they should have lived to 180 specifically. However, answering why one of them should have lived to 180 and why all of them should have lived to same age will serve as an answer to my question.