Your conclusion relies on a missing value for the unknown period in which the joke was not yet old. Maybe it was funny for the first five years, and they are now 35 years into their hike.
Correction: correctly used apostrophes save lives. When apostrophe’s are used for plural’s instead of possessive’s and person/tense marker’s on verb’s, chao’s ensue’s.
♫ I’ve got a bike♫ You can ride it if you like♫ It’s got a basket, a bell that rings♫ And things to make it look good♫ I’d give it to you if I could♫ But I borrowed it
Mommy, why is that man’s TV so fat?