Another thing you can do is wrap a wet paper towel around the severed end, and a plastic bag covering that, and a little higher up if the shape of the produce still allows some airflow past that point, then you check and keep the paper towel wet.
This continues to hydrate the produce, like lettuce, celery, asparagus, broccholi and cauliflower, and to some extent other leafy things like cilantro (but not as much, it's better put in a cup with water even if not in a drawer).
Which strategy works best for you includes both the age and treatment factors that Steltek mentioned, but also your rate of consumption, how old it gets once in your custody.
Frankly I would not sweat the lettuce as much as other produce that is more nutrient dense and more expensive. If my lettuce isn't crunchy, there's always onion/crouton/bacon/radish/carrot/etc crunchy things I can add to keep some good texture in a salad... but I'm a savage, I actually add random dandelion weed leaves to salad too, just pull the whole plant to get rid of it before it spreads and eat it. They are a little bitter, I keep that in mind when selecting the dressing.