“Should all young men who are worthy go on missions?” Ensign, Feb. 1974, 38
The scriptures speak of missionary service more in terms of an expression of the soul than just a particular period of time.
“Therefore, if ye have desires to serve God ye are called to the work” (D&C 4:3) might well be a call to all Church members to serve God by thinking and praying and acting like missionaries in their everyday lives.
The admonition “… it becometh every man who hath been warned to warn his neighbor” (D&C 88:81) can and should be fulfilled by every family in the Church through friendshiping a nonmember family until such time as the hearts of that family are ready to hear the gospel. Then they can be taught by either stake or full-time missionaries or the two working as a team.
When a young man approaches the age of 19, he should be interested in preparing for a full-time mission, both spiritually and financially. He should go if he is worthy, if he is emotionally and physically able to stand the rigors of full-time missionary service. In this context, every able and worthy young man should be willing to go on a full-time mission providing his local priesthood leaders recommend him and the Lord through the President of the Church extends the call.