I recently vacuum packed 1 kg of coffee beans that were about to expire into 100 g portions.
I would like to know how they will be affected by the freezing and how long they will last in the freezer.
Freezing will not affect the coffee beans chemically. Thawing may affect them though.
When you thaw the beans, small amounts of water (that were frozen as small amounts of air humidity) will melt and it may collect together and cause some very small extractions in the bean. This is probably quite minimal due to the fact that you have vacuum packed the beans though. This is generally undesirable but it is up to you whether or not you want to do this.
If you do indeed freeze them, make sure that you let them thaw completely before opening the package. Do not open the package until they are back to room temperature. This is so that the humidity can stabilize inside. If you open the package earlier, moisture from the air may condense onto the beans, causing a small amount of extraction.
In terms of how long they will last in the freezer? I am unsure of this as I have never frozen my beans as it is not recommended.
It should be ok, but freezing the coffee beans for the long time is not reccomended. It is a good way to store but do not re-freeze them many times. In the freezer they are supposed to last for quite a long time, but hard to say how much since they are old already