If you are more efficient in your direct mailing strategy it could potentially get closer to the real target audience. If it has more targeted list your list size will shrink, but so does your postage costs and your lead generating campaign will soar.
It is good to see that there will be an increase in the response rate of your marketing efforts because that correlates with increased sales and revenue.
You need to invest in the list, in the database of contacts. Most marketers would say that 50 % of the marketing success is in the list, the list of target audience. When you make the effort to restructure your database, you'll get the most value for your marketing asset, and will make you more efficient in winning more sales.
Take the time to review and determine which company can help you achieve your dreams and business goals. Hire a company who can create that database for your business and see how it will help increase your future campaigns.