Well, the body does adjust to things. It happens with pain medication and blood pressure medication. Tolerance.

With some vitamins a "dependency" state can result. Meaning the body gets used to higher doses and then expects them.
It happens with Vit C... those taking high doses, for a period of time may actually develop scurvy when going off them.

This may vary with the doses taken. This is why I don't recommend really high doses except for B12 which is very critical and needs it when people are low.

By keeping doses in the average range, one can avoid "dependency" issues if they are going to manifest.

It is a fine line for each person, because we don't have the technology to monitor people on supplements well. That line may vary in location depending on the person.

There is also a placebo factor which may be at work. But I find that it is most likely in those who have very fast responses to supplements, which typically take a longer time to show benefits. Taking a supplement and getting results in a few hours, suggests to me a placebo effect in the beginning. Most supplements are correcting a long standing difficulty, involving many enzymes and chemical reactions, and those typically take some time to correct themselves.