In light of the other thread, I find this an interesting question, as well. I'm a prolific reader of science fiction, and several authors have dealt with this question: How long will believers wait before losing faith?
It's been 2,000 years. At what point do you believe that Christianity will lose faith in Christ's return? Never? In 1,000 more years? In 5,000 more years? What impact does the non-returning of Christ have on the belief system?
After all, it's been predicted hundreds of times, to no avail. Would we have any reason to believe that it actually will occur?
His return is unknown as to time and place. Someone will believe forever if it never happens.