no matter how much money i would make, you will never see me flying first / business class before i'm 40

you can use the funds in like 1000 more productive ways than buying comfort for a few hours

a cost of one first class flight can buy you a year of workouts with a personal trainer which will delay the necessity for sitting in the first class for another 5 years

pure destruction of capital

being over 40, 6'2" and not able to sleep at a not so upright seat position, the rare times I got an upgrade, it was totally worth it. Otherwise, it's usually cheaper to arrive a day before to the events planned for the trip and dedicate this time to proper recovery,..