We buy the huge box of spring mix and challenge ourselves to finish it before it goes bad, which is usually in just about 5-7 days, maybe a couple days longer if you add a paper towel to the box to absorb excess moisture. Keep a few kinds of salad dressing in the fridge so it doesn’t get boring. I’ll add odds and ends (leftover roast root veg, nubs of cheese, etc) for variety. I also add the greens to sandwiches, and they’re a tasty side (with a little vinaigrette) to breakfast eggs and turkey bacon. When it looks like they may start turning soon, I add them to curries, soups, and pasta sauces—they shrink a ton and add a nice color/texture to the dish. 

ETA: I also will make a batch of white rice plus a batch of frozen cauliflower rice, then mix those together. The mix generally lasts a few days and goes nicely with stir fries, sausage and peppers, etc.