Student Visa, zairyu card address registering

Hi everyone,

I'll be in Japan as an exchange student for one semester. I'm moving into the dorm of the University on 22 March and moving out on 31 July.

Before booking plane tickets I checked with the Consulate and my exchange University about when I could enter the country and when I had to leave.
My University told me I could stay on student visa until the 20th September, since that's when the official academic date for Spring semester ends. They told me to go to the embassy/Consualte about the arrival date.
The Consulate told me I could enter Japan as soon as I had my visa, and from then on leave within one year (I was issued an one year visa).

So now I have booked my ticket and I will arrive on the 7 March and leave on the 3 September.

I already booked an airbnb in another city for 7-22 March, and I understand that since I'm staying longer than three months, I will receive a zairyu card and that I should register my address at the city/ward office "within 14 days from the day on which he/she decided the domicile (or for a mid- to long term resident who had already decided his/her domicile, from the day on which he/she obtained the said permit)"

[from http://www.immi-moj.go.jp/english/tetuduki/juukyoti/tyutyoki.html]

Since the airbnb is only for 15 days, do I still have to register and then notify the city again of me moving out and then register again in the other city, or would it be enough to only after moving into the University dorm?

Also, after moving out of the dorm 31 July, I intend to travel around a bit and staying at different accomodations. Do I have to repeat the address change procedure?

This got quite long. Thanks for reading and I hope you can help me.