I am an advocate of building up to the distance and intensity needed for an especially long ride. And if done right, I am not needing anything special but some sleep and maybe 1- 2 days rest.
OTOH, if I am not sufficiently fit fo the load, it might take 3-5 days to recover. The problem is plasma volume and stroke volume will start to significantly decline and fitness is lost. So, I try to do some easy Z1-Z2 rides and take hot baths with the old skool self massage to the legs.