My sims first butler was not great, but now my sims have an amazing butler. So I think it's good to fire them until you get a good one. The butler my sims have now does everything I want her to do--she cleans right as things get dirty (clears plates from tables right when my sims finish eating) fixes things, and helps out with the toddlers only when the parents are busy. She even showed up to my sim's first piano recital like a proud grandmother. When she dies :(, they'll probably have another bad butler.