It's good to bridge extrinsic to intrinsic motivation as the long term achievement will be more rewarding. 

I teach students from 17-60 years of age, and you can definitely see a difference from the younger learners to the older adult learners. The older learners seem to take things more seriously and try harder and don't miss as much class time as the younger ones who may still be living at home with their parents. Possibly the older learners have more to lose than the younger ones and have already developed a good sense of security and autonomy.