I found the statement amazing and completely unbelievable. I'm not trying to be a pessimist, but I wondered if he and I were reading the same Great Commission.
Matthew 28:18-20 says,
Then Jesus came to them and said, “All authority in heaven and on earth has been given to me. Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.”How can that be accomplished in a lifetime; let alone 10 years?
It seems he may be confused with the popular understanding of "sharing the Gospel"as the Great Commission. Getting someone to pray the "Sinner's Prayer" or just having them hear "the Gospel" has replaced "go and make disciples" as the call of the Great Commission.
Jesus calls us to make disciples not acquire conversions. The problem with conversions is that so many of them are completely inauthentic. There is no real desire to love and follow Jesus...to be transformed and pursue Christlikeness. The real desire often seems simply to avoid hell or make it into heaven when we die.
Being a disciple is so much more difficult...and it isn't always fun. We have to pursue a life of obedience and holiness...taking up our cross...being persecuted for righteousness...stuff like that.
Conversion is often the easy part...disciple-making...that is difficult.