That is a great question and I agree with what Dan has stated. In general, this is the case. Of course there are exceptions like Jack Passion who certainly grew bigger and longer than two years.

Now for me, I have been growing 27 months and my beard is still growing. But my hairs are of varying lenghts and consistencies depending what part of the beard from which they are growing. The neck hairs are the longest and growing the fastest. I think that my soul patch area is at terminal length. No more growth there. The chin hairs and even stache hairs are still growing, but at different rates and slower than the neck hairs. I do not yet know where my terminal length will be. So if I trimmed off my lower beard, overall it would keep growing as the slower hairs would now catch up. This act would have the appearance of thickening up the lower end of my beard at the sacrifice of some length, at least temporarily, until more hairs grow longer again and the slower growers keep growing.