No, I always leave story progression on, it adds a kick to the game.
Turning aging off and leaving story progression on is a
really bad idea, as the two are quite literally linked with each other. What you're not realizing is that the "kick" this is giving to your game is square in it's guts.
Your towns (WA locations included) can only hold so many Sims. When you install the game, it decides on numerous things based on your computer specs, and the number of townies is one of those things. When the population surpasses this limit, the game will remove Sims from the town in an effort to keep your game running at optimal performance. It does this by either killing Sims in an "accident," or moving them out of town.
When you turn aging off without turning off story progression, Sims continue to live their lives as normal: they find jobs, they quit jobs, they form relationships and have babies. The one thing that they
don't do is age. This means that any new babies that are born/adopted will stay babies forever...but they still count as a Sim for purposes of determining how many Sims are in the town. So once this causes the number of townies to surpass the designated number, townies will either die in a tragic accident or move out. If an adult dies/moves, it will never be replaced by another adult...but since the number eventually drops below the designated number of Sims in town, it allows
more babies to be born. And once the number of townies surpasses that magic number again, the process repeats itself.
While babies can die in these "accidents," they cannot move out without an adult (meaning that if you lose a baby in this way, you
also lose an adult). Thus, when the game initially decides to remove Sims, the chances are dramatically better for an adult to be removed than it is for an eternal baby to be removed. So after a while, infants in town will outnumber the adults. Infants cannot fulfill the roles of co-workers/schoolmates, friends, and will not be able to give you opportunities (including quests).
This could very well be the heart of your problem.
Doing the opposite is equally bad: Sims age and die, but are never replaced by a new generation. New families will move in, but it seems that these families will be fewer and farther in between as the generations continue. It removes the legacy of the townies, and will eventually turn your game into a ghost town.