One upon a time, I was at a dinner my university threw to bring together scholarship sponsors and scholarship students. I was sitting at the table with Mr. M, of the Mr. and Mrs. M that were paying for much of my education. Mr. M was quite successful in the construction business and was bankrolling over a dozen engineering students that year. He was in his nineties at the time. [Edited to add: I just checked and it appears he passed away this year. I'm going to send his family a card after I get home from work.]

Anyhow, at one point, my college nemesis (also, through accident of fate, at my university through Mr. M's generosity) was doing his usual intellectual preening and mentioned some numbers he had been working on for his civil engineering project. As I recall, it was how much reinforced concrete he would be needing for some project or other, but don't take my word for that: if physically exists it is Not My Department.

Mr. M mentioned, in a humble and offhanded way, that perhaps Nemesis should consider adding 20% more reinforced concrete so that the structure at issue wouldn't fail.

Nemesis: "Well, I don't know where you're getting your numbers, old man, but in this day and age X is considered enough."

Mr. M: "Well, I suppose it is entirely possible they have improved on the formula since then."

Nemesis: "You mean since you used it last?"

Mr. M: "I mean, since I invented it."