Kinda bad they never really tested this part of the game.
Let's consider this for a moment:
How big do you think their quality control department is? 50, maybe 100 people? A couple hundred at the most.
Now...how many
players are there? A bit over 7 million worldwide.
Let's assume that the players play a single hour a day and EA has 1,000 play testers who worked double shifts (16 hours a day): even if EA tested their expansions for an entire year (with no days off or vacations), players would still log more play time in a
single day than there was testing time overall.
The fact of the matter is that it's impossible to test a game as thoroughly as people want them to. Games are quite a bit more complicated now than they were in the heady days of 8-bit. When you make software more complicated, there is going to be more bugs...and as far as the volume of background operations goes, Sims 3 is one of the most complicated games ever made. It's little wonder that it's as unstable as it is.
Even console games need patching these days. Diablo 3 has been "in production" for somewhere around 5 years, and even if they finish out the decade play testing it before they release it, I guarantee you it's going to have bugs that they didn't find. It's the nature of the beast, and the only way you're not going to have to deal with bugs on some level or another is to not even touch a computer.
In answer to your question: the singer I played for writing the Singer article had 4 steady gigs by the time she reached level 10. All 4 showed up in her schedule, and she has played at all 4 of them at least a couple of times without issue. In fact, the only problem I
did experience was cancelling them.