What retirement plan are you provided with and when does a missionary retire?

Each missions organization has different retirement plans just like each business or company has different retirement plans.  We work for Youth With A Mission (YWAM) which is a grassroots missions organization that is decentralized and allows each of its regions around the world to choose how it handles retirement.
As a Canadian YWAM'er, who pays Canadian income tax, we are legally considered to be "self employed contractors" who work for YWAM Canada.  YWAM Canada has no retirement plan and only takes a small percentage of our missionary support to cover accounting and office expenses.  Each Canadian YWAM'er has the freedom / responsibility to plan for their own retirement.

"When does a missionary retire?"
There is no planned retirement in YWAM.  Each missionary makes that decision on their own depending on what God tells them, their health and family situation.
Our international leaders model a lifelong calling to missions and most of our senior leaders continue their full time missionary work well into their 80's.
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Unlike some professions missionaries, and other christian leaders, usually become more valuable as they grow older (a very eastern cultural concept).  Their experience and wisdom become invaluable as they have been learning and growing for so many years. Unlike some jobs, such as those that deal with technology and things that change rapidly, christian leaders do not become obsolete over time.  God and His relationship to Humans is an everlasting subject.

​How do missionaries prepare for retirement? Or do they? Have you met missionaries who don't retire? How are missionaries provided for ?

Some of this questions was answered in my response to question #1. (To recap: YWAM missionaries prepare for retirement however they want whenever they want. Yes, I meet many missionaries who never retire)

Here is my response to the last part of the question.  "How are missionaries provided for?" I will answer this question as a Canadian missionary since that is my context.

Most Canadian missionaries prepare for retirement the way that an average Canadian would.  Our family has a small amount of RRSP savings and we always pay our CPP contributions when we pay our income tax to the government.  
The difficulty for us is that we always seem to have pressing needs and almost never have money to put into our RRSP account.  When we need to choose between putting a couple of thousand dollars into our retirement account or travelling to another country to teach people about the bible, the bible teaching always wins.
From a financial point we are not very well prepared for retirement but we have been living by faith in God since 2003 and believe that God will continue to provide for us into our old age.

​How do you teach your children about 'real' life? (As in: going to your job, earning your money, school culture, etc).