This might be kind of out there... but, In season 3 the Safety Training episode Darrel says you only have to do the training once a year, but they never make it a full year without an accident.
But in season 2, the Boys and Girls episode there is a chalk board that says they've gone 936 without an accident.
That's a lot more than a year...

Sorry if someone has already brought this up or maybe it's just stupid. I just wanted to point it out I guess. Yep...