Great answers so far, here's my take
1) There are some great charts for this. Check out Doug Baldwin's site, he's one of the guru's of SV time and temp. James Logsdon has great info on cooking time by thickness. I've used the foam tape to run a probe into the meat through the bag, but don't bother anymore. Once you know time by thickness it's not necessary.
2) You can cook too long. Food can degrade too much and get mushy. But the margin is very forgiving. However, I recently cooked a pork loin at 145 for 10 hours. It got too soft and lost too much moisture. Less time would have made it much better.
3) Any time you cook meat close to it's serving temp, rest is not needed. However, if you are going to sear it's a good idea to let it cool a bit so you don't overheat during the sear. For some food, I'll chill in an ice water bath first
4) Most food benefits from being held at temp for a certain amount of time to help tenderize it. Things like short ribs, brisket, etc, will hit internal temp within hours, but can take days to reach optimum tenderness. Fish and some veggies are some things that often don't need additional time once they hit temp.
