The key for me is making sure the lettuce is really dry. I spin it, leave it in the spinner colander (same spinner linked to above and mine is old also) and then put the colander in the refrigerator on a towel to dry out for a few more hours. After that I put in a regular plastic container. Mine is a 12 cup rubbermaid container for dry good and I pack it tight with lettuce to make it last *almost* a week. I like that container because it is tall and slender and it is always in my fridge. (I also have cleaned spinach or kale in a separate container to add to salads and make it last longer. I can get 6-7 days out of the combo.) If the lettuce is still a tiny bit damp, I will lay a paper towel on top and then remove it the next day. I chop toppings and put them in a separate container.
I have done the mason jar salads and they work well especially for individual lunches or dinners. For us, it isn’t a great fit. I eat salads everyday for lunch and typically add leftovers to it and then we have different salads for dinner every night depending on what is in our garden. Dh and one DC eat salad. I need to be able to adjust to it is easier for me to just have lettuce ready. (eta: I also don't like tomatoes refrigerated.)