The younger generation challenging the older is a popular and well-used theme. This timeless conflict provides ordeals for the children standing up to the parent(s), and the guardian experiencing his/her own mortality when they remember similar episodes with their own parents. This generational drama can often be found on the page.
Fairy-tale struggles with wolves and witches may be ways of expressing those same conflicts. Notice how "dark" figures are often the experienced characters pitted against the "newcomer" or child? Ex. Little Red Riding Hood, Hansel and Gretel, etc. Joseph Campbell spoke of the dragon as a Western symbol of a tyrant who has held fast to a kingdom or a family until all the life has been squeezed out of it.
The age conflict can be experienced internally as well. The plot conflict may arise from a struggle between an old and comfortable lifestyle, and a new, unknown and untried one. The new self can't be born until the old one dies.
Science Fiction - Fantasy authors use a similar technique in time travel stories. Will the hero return to his/her own time, or will they be better off in the past/future?
In some cases an Ordeal can cause a healing of wounds between a hero and parent. Campbell calls this possibility "Atonement with the Father." Sometimes a hero, by surviving an Ordeal or by daring to challenge the authority of a parental figure, will win the parent's approval and the seeming conflicts between them will be resolved. Ex. Sister Act II: Back in the Habit
What are some of your favorite examples of age conflict?