To start, high-quality wood fillers typically do not shrink during the drying process. However, it's crucial to follow the recommended maximum amount to avoid this issue. For instance, if you apply an excessive amount of filler into a 1/8-inch wide and 3/4-inch deep crack, the filler will dry on the surface but take an extended time to harden in depth. This is not a recommended technique. It's better to fill in the crack in two or three stages to prevent the surface filler from cracking.