Well, I've often said that games as large and complicated as Sims 3 or Skyrim will naturally become buggy. And typically with those two games, I play the characters until something finally breaks. The problem is that, in the case of Sims 3, I have never-- not once in five years-- had a sim family make it past the second generation. Almost all sims games I start, I intend to take them multiple generations, sometimes even planning out what I want to do with the kids and grandkids... and not once have I ever had a game last that long before it completely bugs out.
I have had situations like this where the interface completely craps out. I have had sims completely removed from the game (not just "invisible", but GONE). I have had entire buildings disappear. One creepy time, I got back from China, and all of the townsfolk NPCs were gone; it was spooky like Roanoke.
So with a game this size, that tries to take on this much, I expect that things will go wrong before I fully get to play out my intended characters... but when it happens this often, this regularly, in this many different ways, across this many different years, mods, patches, expansions, and PC builds... eventually you have to wonder if this is me being impatient, or if the game was simply never programmed well.