Eruvin 54a says that it was taught by Rabbi Eliezer ben yaakov that wherever it says Netzach, Selah, or Vaed it means it will remain so forever. "כל מקום שנאמר 'נצח' 'סלה' 'ועד' – אין לו הפסק עולמית" ...
Eiruvin 13b records two years-long disputes between Beit Hillel and Beit Shammai, and surely these are not the only long-running debates. How did that work in practice? Did they really have a single ...