How long will you be gone?
A; Could I borrow your car?
B; What's wrong with yours?
A; It's got a flat tire.
B; How long will you be gone?
A; Just for an hour or so.
B; OK, Go right ahead, Drive carefully.
A; Don't worry.
A; How long will you be gone?
B; Only for an couple of days.
A; Have a nice trip.
A; How long has he been gone?
B; About half an hour.
I expect him any minute.