I worked in a kitchen at a retirement home for too long it made me aware of the rubbish they say but my understanding is that you only need really worry about being careful if your feeding the very young or very old, ie. Weak immunity. As said if it looks ok/smells ok that's a good enough indication but I won't touch chicken that's been sat all week, also if something's been sat in a warm, sweaty, hasn't been cleaned for months microwave, overnight, I can't help but think of all the bacteria multiplication that's happened (bacteria doubles every twenty mins at 36 odd degrees) also if the food gets left out the cats normally find it and muller it, won't touch it then lol. But generally, keep it cool and if it don't grow legs and walk off it'll be ok.