D&C 107

Concerning the Seventy, the Lord instructed -

"...it is according to the vision showing the order of the Seventy, that they should have seven presidents to preside over them, chosen out of the number of the seventy;
94 And the seventh president of these presidents is to preside over the six;
95 And these seven presidents are to choose other seventy besides the first seventy to whom they belong, and are to preside over them;
96 And also other seventy, until seven times seventy, if the labor in the vineyard of necessity requires it.
97 And these seventy are to be traveling ministers, unto the Gentiles first and also unto the Jews."  (Doctrine and Covenants | Section 107:93 - 97)

But then He adds -

"Whereas other officers of the church, who belong not unto the Twelve, neither to the Seventy, are not under the responsibility to travel among all nations, but are to travel as their circumstances shall allow, notwithstanding they may hold as high and responsible offices in the church."  (Doctrine and Covenants | Section 107:98)

Where general authority Seventy are to be traveling ministers, there are now Area Seventy that are officer as high and responsible where travel is limited to their circumstances allow.