Earlier quoted context omitted.
I think you're confusing forever with a really long time. (1) Asteroid's velocity is eventually overcome by external forces. (2, 3) Structure decays. (4) Bodies converge or diverge. (5) Radioactive decay. (6) You are observing a high energy system. (7) Etc.
I don't think I'm confusing forever with a really long time; I'm just assuming they're effectively the same. (Aside: nothing exists forever - even time crystals - because eventually the universe will be a bunch of infinitely far apart black holes or something. So I'm not sure how that assumption is relevant.)
In addition to that, the tidal forces will compress and decompress the mass of both objects, which effectively converts potential energy (the distance between the two objectds) into heat. Even though the moon is on a trajectory to eventually leave earth orbit, every tide that comes in and leaves lowers the rotation speed of the moon. While the moon has no liquids on it's surface, which makes the effect nearly invisible, it does have tides (slight variations in the angle and magnitude of gravity at it's surface) which move objects around and the energy for that does indeed come from orbital decay. Similarly, the earth loses orbital energy to the sun.