The damge/degradation wine suffers after opening primarily comes from oxidation. The secondary purpose of decanting (after separating clean wine from sediment) is to aerate, that is oxygenate, the wine.
Once in the decanter much greater surface area of the wine is exposed to the air.
I don't like wines the next day anyway, but left in a decanter they lose even more.
Best idea - drink your best wines in one sitting.