Quotes from Elder Hinckley at the 2011 Seminar for new mission presidents, published in Church News 9 July 2011.
"Senior couples are 'under-utilized assets'"
"...the total requests by mission presidents for couples has been as high as 3,200 couples or 6,400 individuals... Currently about 1,900 couples are serving. That means approximately 40 percent of the needs of missions are left unmet... Rarely a week goes by that I do not receive a desperate phone call from a mission president begging for more senior missionaries."
Recent changes for senior or couple missionaries:
1. Couples may now serve for 6, 12,18, or 23 months. They may serve outside their country of residence for less than 18 months if they pay for their own transportation to and from the mission.
2. Couples may at their own expense take a short leave of absence from their mission (normally no longer than 7 - 10 days) to return home for a critical family event.
3. Effective 1 September 2011 a cap of $1,400 per month will be established for housing costs, that is rent, utilities and furnishings.
Expanding on #3, from lds.org: Missions, temples, or area administration offices now will locate and secure appropriate housing and pay all housing costs (including rent, utilities, and furnishings). Missionary couples will then reimburse some or all of those housing costs up to the cap.
Missionaries from the United States, Canada, western Europe, Japan, and Australia will be expected to reimburse the cost of housing up to the cap, while those from all other countries will be expected to reimburse the costs up to their individual ability to pay (but not to exceed $1,400 a month). Couples will continue to pay for food and other personal expenses.