When can I safely say 「行ってきます」when leaving home or another place? How loosely can this phrase be used? Can you use it even if you don't plan to come back until a day/week/month later?
If it is going to be an extended period that a person is gone (from home), is there another a better phrase to use or is「行ってきます」still appropriate?
For the sake of the question, let's assume that the listener knows that the person is leaving, and they also know how long that person will be gone.