For safety I would not alter anything from food cooked using conventional methods and stored in plastic bags or containers.
For the different types of food the same recommendation.
This is not based on any study I have seen but rather on what I do. Thinking about the meals I make I rarely have leftovers unless I am making a roast. Everything else is cooked using portion sizes for two plates worth.
I have not found a need to rest anything. Resting is important when you cook a protein at a high temperature. The juices are driven towards the center while cooking and resting gives them a chance to redistribute. When cooking at low temperatures the difference between the center and the outside is so small juices remain well distributed.
@RTcooking the only thing i would recommend differently than @john.jcb is, if your going to be finishing by additional cooking ie searing in a pan, keeping a bowl of ice water handy to lower the exterior temperature might not be a bad idea. Alternatively, you could put it ibuprofen the freezer for 10 minutes, or submerge rapidly into liquid nitrogen. This will assist preventing any over cooking of the food when you finish. Resting at room temperature really won’t do much of anything for it.
Extended shelf life is only a consideration for food which is under a ‘hard vacuum’ which would require use of a vacuum packing machine. The long cooking process sterilizes the food and the vacuum sealed pack leaves no ability for microbes to re-infect the sterilized foodstuff. Foods cooked in canning jars should also be safe for an extended time, provided the jars have sealed correctly on cooling.
“The long cooking process sterilizes the food”
This isn’t true. While extended periods of cooking definitely kill off most pathogenic bacteria, there is no way to truly sterilize a food at the low temperatures you’re dealing with using an immersion circulator. The best you can hope for is pasteurization. There are a lot of bacteria that produce vegetative spores, which, even after a long cook in a sous vide set up, are still viable to grow.
“vacuum sealed pack leaves no ability for microbes to re-infect the sterilized foodstuff”
This also isn’t true. Vacuum packs or no, there are bacteria that, if present or their spores are present will grow in an oxygenated environment or an anaerobic environment. Many of the pathogenic bacteria responsible for food borne illness will happily grow in a vacuum packed environment.
Even if you’ve cooked something for a long time, even if it’s been vacuum packed, you still need to observe basic food safety. If you’re not going to eat it right away, you need to get it down out of the microbial “danger zone” as soon as possible, because if there were spores present, they will have survived, and the food you cooked was not highly acidic, they will begin to germinate, produce bacterial cells, and begin multiplying.
Apologies for the incompleteness of my response as I was making the assumption of correct storage of the cooked product at below 4C. Also incorrect selection of incorrect terminology as pasteurisation is, indeed, only partial sterilisation.