There are a number of holly plants that with time, will outgrow the location they were planted in. Holly is typically selectively pruned back in late winter, keeping a natural appearance. This allows for a good berry show. Foundation plantings have a useful lifespan of about 12 - 14 years. You may be at a point to consider replanting. Plants that naturally grow larger than we want will end up being very woody as we struggle to maintain the size. Plants have to grow in size every year and will again be larger than you desire. If they are well along already this spring, it is really too late to cut them down. For a more local perspective on your question, you should contact your local extension office.