For the past few years I have taken on a fairly ambitious reading project. One year I read Calvin's institutes. Last year it was Grudem's Systematic Theology. This year I am reading some volumes of Spurgeon's sermons. I am also reading a biography of Spurgeon.
Spurgeon was a man who wanted to be useful to God. He was perfectly content to pastor a small church. But God had far a larger ministry in store for Charles. He ended up pastoring a "mega-church" in London for most of his adult life. But Spurgeon's ministry was not limited to his church, or even to his century (the 1800's). Many of Spurgeon's sermons were printed and published. Eventually many of these sermon's were published together as a series of over 50 large books. They are still available today, and many sermon's are available on the Internet.
My dad gave me five volumes of Spurgeon's sermons. I began reading volume 19 in December (of 2009). There are 61 sermons in 732 pages- not short pages by the way. The first owner of this particular book, Rev. George Headley, Jr., inscribed his name one the first page of the book. Rev. Headley was my dad's pastor and mentor when Dad was in college. From notes left in the book it is obvious that Pastor Headley was benefitting from Spurgeon's writings as early as 1972. Below Pastor Headley's name is the signature "Rev. Jack Peters 10-92." The marginal notes on some of the pages were obviously left by him. Curiously, he noted at the end of one message that he had read that particular sermon after PRM (Prayer Meeting?) on 10-16-91. So Dad owned and benefited from the book sometime in the early 90's. Now I am reading and quoting from this same book almost twenty years later.
I doubt that Charles Spurgeon expected that sermons he preached in the 1800's in England would continue to benefit pastors and their congregations in the 1900's and 2000's in America. By God's grace, that is exactly what happened. Three pastors and their congregations have made use of just one copy of one book. You may not feel that the things that you are doing will have much impact on anyone. But because of God's grace, you never really know how God will use your work to serve people you aren't even intending to serve. So be faithful. Continue to serve. And leave the long-term impact of your work up to God.