The duration for soaking dishes in cold water before washing them can vary depending on the type and amount of residue or food particles stuck on the dishes. Cold water is generally effective for soaking dishes with light to moderate soiling, but it may not be as effective as warm or hot water for grease and tough stains.
As a general guideline, you can soak dishes in cold water for about 30 minutes to 1 hour. This should give enough time for the water to help soften and loosen the dried-on food particles, making it easier to clean them during the washing process.
If you're dealing with particularly stubborn or greasy stains, you may want to consider using warm or hot water for soaking. In such cases, make sure the dishes are safe to be soaked in hot water to avoid any damage.
Remember that if you leave dishes with food residues sitting in water for an extended period, it can promote bacterial growth, so try to avoid leaving them soaking for too long. If you can't get to washing them immediately, it's better to rinse off the excess food debris and then soak them for a shorter time when you're ready to wash.