I recommend reading this very thoughtful article by Tony Miano. My only beef with it is that Miano is mistaken when he invokes an “any moment” rapture as a motivation for evangelizing the lost to come to Christ. Scripture never teaches imminence, let alone a motivation for coming to Christ. What Scripture does teach as a motivation is the certainty of his Return and the consequences for the unbeliever being spiritually unprepared to meet the Lord. That is the consistent warning from Jesus, Paul, James, Peter, and the book of Revelation.
Nevertheless, may the article motivate you to have a sense of urgency for kingdom-work:
http://www.onthebox.us/2012/06/christian-where-is-your-sense-of.html