You can bank all the way up to the 8th month of the current UY. Since your March 2022 UY goes from March 1st, 2022 until February 28th, 2023, the banking window is until October 31st, 2022.
You can not bank the points until the UY actually starts. For example, if you decided you wanted to bank your March 2021 UY points, you can’t do it until we get to March 1st.
You also can bank as many times and in any amount during the 8 months. It does not have to be in one transaction or the full amount.