I have an iMac that first came out 2 years ago, and I do not notice either fan roaring or jumping and jittering. Is your experience with this on the laptops?

I have an iMac that first came out 2 years ago, and I do not notice either fan roaring or jumping and jittering. Is your experience with this on the laptops? (I do, unfortunately, notice that the fan sometimes goes to medium in the middle of the night for no apparent reason. It's not quite annoying enough to shut down when I go to sleep, though).