The reason the angelic heaven is an image of what is infinite and eternal is that it is an image of the Lord, who is the Infinite and Eternal One. We can see an image of his infinite and eternal nature in the fact that there are millions of angels who make up heaven, and that they make up as many communities as there are general desires of heavenly love, with each individual angel in each community being quite clearly his or her own desire. The form of heaven is made up of all these general and specific desires, a form that is like a single being in the Lord’s sight just the way a person is a single being. This form is becoming more perfect to eternity as its numbers increase, because the more people there are who are participating in the form of divine love, which is the form of forms, the more perfect is the union.
We can see quite plainly from this that there is an image of what is infinite and eternal in the angelic heaven.
from Divine Providence, Section 62
Secrets of Heaven 