Sorry, I'm having a brain fade here. Are you talking about the time required to make up for lost earnings (and ignoring that the current 112k is not a fixed amount the way a salary generally is)?
With all that said. There is definitely some survivor bias here. He found a great niche and a appears to already have had an audience which helps tremendously compared to starting from scratch. Not everyone will have the same success experience.
Hoping I can get a similar thing going in the near future.
I mean, the math is very much simplified. People get raises, and change roles, and there's tax to deal with, and jobs have benefits, etc. The core point is that you'll probably earn a lot more in a job. If you can find one where you're paid to maintain a library you like that's probably better for you financially than trying to get sponsors.
There are many reasons why quitting your day job and growing a presence that will get you sponsorships is worthwhile, and I am a strong advocate for paying open source devs who maintain the packages you use. However, if you're thinking of trying to copy Caleb's success, remember that it'll take 28 years before he'll have earned more than he would have if he'd kept his $90k/year job.
Arguably a talented dev will never earn more than if they'd had a job instead. Open source is a route to working on something you love, but you will be leaving money on the table to do it unless the landscape changes a lot.
There is still a ton of change necessary in the open source model before it becomes a viable 'job' for most people.