In my main town, I have 100 neighbours, so I usually get rid of all my terrors, but I also see that it don't take many hours of not playing before I have over 100 new terrors, so if I can't play one day, for any reason, I'll soon pass 500.
In my other town, I only have like 10 neighbours, and often when I wisit them, their town is already full, so I'm passed 200 terrors now, and I don't see how that number's going down any time soon if my neighbours don't start playing more often.
So number of terrors don't always depend on how often you are playing yourself, it also depends on the number of neighbours and how often they are playing. And some of them might have problem logging in or getting thrown out when wisiting neighbours. Or they just think that their neighbours have reached all goals, and are afraid they'll be irritated if they get more terrors untill the next act starts.
