И у самого длинного дня есть конец
See После грозы - ведро (77)
Cf: Be the day never so long, at length comes evensong (Am.). It is a long road that does not end (has no ending) (Am.). It's a long lane (road) that has no turning (Am., Br.). It's a long line that has no turning (Am.). Long as the day may be, the night comes at last (Am.). The longest day has an end (Am., Br.). Tis a long run that never turns (Br.)
Русско-английский словарь пословиц и поговорок.
Академик.ру.
2013.