Loss of quality when rendering?

I was told that everytime a project is rendered it looses a bit of quality. Is this true?

As a general rule, yes. But it is possible to reencode and produce a better video. Lets say you capture an avi file from a fairly noisy source. In this case, you can use virtualdub and a denoise filter to produce something that has less of the original information, but actually looks better.

I guess you are using something like Premiere, which I also use quite often.
Some big projects with complicated stages, and re-editing etc seem to get re-rendered several times before I´m finished, but to be honest, I´ve never noticed any significant loss of quality.
But, like a jpeg, there is going to be some loss every time you open an image, work on it and re-save it. Is there anything that can be done to avoid this?

Deanimator, that is why I am aksing because in the past while working on projects I would like to render them, then maybe later, edit and rerender. But If im going to lose qaulity everytime I will have to focus on only rendering once.

P.s. I am using Sony Vegas.