Can/should you re-use engine components?

I have learned the hard way that while something is apart, replace things. It's like when you replace the timing belt on a Mopar 2.2 or 2.5 4 cyl engine; the water pump is right there under the belt. You have already spent hours getting to that point, so replace the water pump even if it is working. I would never put an engine back together with the old timing set. If you flat out can't afford it, that is a different matter.