The driftwood will continue to leach Tanins and could take months to yrs depending on what type and the size of the Driftwood.When soaking driftwood to remove tannins, does it help to change the water every 24/48 hours? The water right now has a very light coloration like a diluted scotch whisky after 24 hours. I can clearly see the bottom of the pale at 18 inches deep.
Usually when I get rocks/driftwood, I boil it and that removes a lot of the tannins if not all, but those pieces are small and are able to fit all the way or halfway in a large pot.
The bad news is that if your piece of wood changes the water colour to the extent you describe in only 24 hours, I suspect you will be waiting/watching/changing water for a long, long time before the leaching process begins to slow down much...
A study has shown that Tannins are a natural stress reducer for even hard water fish.