Simply put, does a spell caster know how much time is left until a spell they cast expires? For example, if Espio the spymaster cast Disguise Self (PHB 233) to infiltrate a city, would he know how long until his disguise wears off? Or is he left "in the dark" until it expires?

Currently, I can think of 3 possibilities:

1. **Precision Knowledge:** Espio knows precisely how much time remains.
2. **Imprecise Knowledge:** Espio has a vague sense of when the spell is running out, but not exactly when it will (think a yellow traffic light).
3. **No Knowledge:** Espio doesn't know how much time is left.

I would prefer RAW, but anything logically argued would be appreciated as well.