There's a similar thread here: http://answers.ea.com/t5/The-Sims-4-Bug-Reports/Meals-at-public-venues-bbq-s-and-spawn-timers/td-p/3520273 but since you say it also stops on your current lot, then something seems off.
Does this happen to new games too if you start one for testing purposes ?
Yes. It has hapened with every new game I have played. It takes a while before it happens though. When I go to a new zone for the first time it takes a while for everything to spawn the first time. After that, everything seems to respawn once a day or so. After a while, nothing in neighborhoods that are not mine will spawn. Then a little while later, they stop spawning there, too.
Wonder what could be causing this. I'm in my 5th generation now and the game is still happily spawning.
I'll add
I'm having exactly the same problem. I read the suggested thread here and a similar one at the Sims 4 forums. Some people had good luck with turning aging on, but that made no difference in my game.
Hi, just to add my voice to say this is also happening in my game. I have aging at normal but have been using the youth potion reward with my sims so they're not aging with the rest of the neighborhood.
Hi again,
OK. I need to report that after 2 sim days of nothing spawning in my neighborhood, the spawners started again after I shut the game down and restarted it (just after I posted the above comment).
I find that a lot of the issues reported in this bug thread (not just this one), like sims not washing dishes and inexplicable poor environment score are solved when I shut the game down and start it again. I can even save from the point things go wrong and not lose any progress, but the issue is resolved when I get back. I have the downloaded game (not disc). Anyway, this doesn't solve the bug, but does allow the player to move on (temporarily). Having said that, some days I have to shut the game down several times a night - so not ideal.
