Under Render Property > Output, there is a choice for you to render the whole sequence out as a video output. I am not sure witch output method is working currently though. I normally render them out as a sets of image files And reassemble them in Video Editor with sound. It’s a simple process.
Like you say depending on HD rendering, each frame can take long time to render; 3 minute at 24 frames per second requires 4320 images to be rendered. If each frame takes 10 minute to render, that will take 720 hours or 30 days! You don’t get to see your film for 30 days if you are rending it out straight. If you don’t like the result of few sequences, it is going to take 30 more days to render out the change!
So when you render it out as an image files to be assembled, minor change can be done quickly. You only render out the scenes you don’t like and replace them.