The two-flight rule is simple enough for a toddler or even a college student to understand: Do not take the elevator unless you are traveling at least two flights up or down. This rule will save you from the piercing stares and eye-rolling sighs of your fellow passengers as you prolong their elevator agony for, like, 20 seconds (!) just so could you avoid walking 12 measly steps.
Yes, we obviously allow exceptions to the two-flight rule for the elderly, people with disabilities, parents with strollers, and buildings where the stairwell is hidden better than a North Korean missile silo or the doors to the stairs lock behind you. But if you have a pair of perfectly good legs and are not carrying a box equal or greater than the weight of an adolescent hippo, you need to take the steps, pal.