I'm trying to render a very heavy scene in Cycles. The scene should have around 10 seconds long. If I render the 240 frames (if it's done in 24 fps) is going to take to much time so I was wondering if I could render it in less than 24 fps and still have a fluid sensation of motion... 12 fps maybe? I don't want to have a stop motion felling.
12 would be your lowest choice but it depends on your animation content. If it has some fast movements they will become jerky at 12fps. For animations; a safe area to start from is 16-20 frames per second. An example is Silent movies which were filmed with a frame rate around this range .