You can keep lettuce in the fridge for about 3 to 4 days before it loses its freshness. Preserve lettuce by not washing it before putting it in the fridge. When you’re ready to use it, simply remove the wilted outer leaves and use the crisp leaves below.
The best way that I have found to keep lettuce fresh is to wrap it in a clean cotton kitchen towel in the fridge. Also, for best results, only wash lettuce leaves just before using. Don't wash all of it and place some damp in the fridge.