Position specific classes(Cubmaster, Den leader, Committee Challenge, Scoutmaster specific, IOLS, BALOO,etc) never expire.  If you took the course in 1950 and have proof you took it (or the comparable course) then it is still valid today.  However, when there are major curriculum changes it is recommended that you take the course again:  recommended - but not required!

Required Training for Scoutmasters and AssistantScoutmasters:  

     Youth Protection, Scoutmaster Specific, and Introduction to Outdoor Leadership Skills

Required Training for Troop Committee Members:

     Youth Protection and Troop Committee Challenge

Below is a list of courses that expire and how oftenthey should be retaken to be valid:

     Youth Protection - every year 
     National Camping School - good for five camping seasons 
     Safe Swim Defense - every two years 
     Paddle Craft Safety - every three years 
     Aquatics Supervision/Swimming and Water Rescue - every three years 
     BSA Lifeguard - every three years 
     Visitation training - every two years 
     Climbing Lead Instructor - every two years 
     Climbing Instructor - every two years 
     COPE/Climbing Inspector - every two years 
     Safety Afloat - every two years 
     Chain Saw Safety - every two years 
     Trainer's EDGE - every three years 
     Hazardous Weather - every two years 
     Physical Wellness - every two years 
     Climb On Safely - every two years 
     Trek Safely - every two years

YOUTH PROTECTION TRAINING

How to see your Training or your Unit's training