I mostly see this as an element to add for the sake of making this one story idea come true.
The basis of probably half of the movies in the "Action" section of any movie rental place is this:
* Person becomes a supreme badass
* Person retires from being a badass and just wants to live a peaceful life harvesting cabbages or whatever
* Bad guys show up and (pick one) kill his dog | blow up his truck | kill his family | kidnap his daughter | burn down his house.
* Person comes out of retirement long enough to kick everyone's ass
Clearly, this should be in the game.
I was thinking something like...
* When dwarves reach a particular age, they retire. If there's an economy in place they may receive retirement benefits.
* Retired dwarves cannot be called back into service. They cannot be assigned to do any work and they cannot be put into the military or given any position.
* During times of dire need, they may come out of retirement on their own. e.g., during a goblin attack, if a certain percentage of the dwarven population has been killed, the retired Hammerdwarf may go pick his hammer back up and head for the nearest goblin on his own.
Ideally, any profession could have "emergencies" that cause a dwarf to come out of retirement, but military would be the most obvious.
Other cases for a dwarf coming out of retirement, though, might be:
* If too much work stays in the queue for too long, a dwarf who had high skill in that area may come out of retirement for a short time (because kids today just don't know the value of work and he has to show them how it's done).
* Something special about a job may bring a retired dwarf out, e.g., it's already a high value dining hall and you assign the walls to be engraved (all the dwarves stand back in awe as grandpa walks in with his engraving kit, gently shoves the young, nervous engraver aside and says, "I'll take care of this one.")
* A particularly dangerous or exotic animal showing up could bring a retired hunter out
* etc