"I begin to feel like I've accomplished my goals. It's like I think that adulthood is something that can be earned like a trophy in one monumental burst of effort and then admired and coveted for the rest of one's life. "
We could have an explicit norm that you can't consider yourself at a given level unless you can pass the relevant test(s) at the time. That seems thoroughly reasonable to me - it allows for saying things like "I used to be at level 6 strength, but I've been so busy at work this year that I haven't gotten to work out hardly at all, and I've slid to level 4".
This sounds good.
Another way to look at it is to say that the levels always come with a timestamp. Once you attain them, you can mentally award yourself a nice badge, like so:

But the badge is only valid for that year; like car tax discs and food truck permits you must keep it up to date.
"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects." -- Robert A. Heinlein, Time Enough for Love
This post is a followup to Leveling IRL. Thanks to SarahC, taryneast, Benquo, AdeleneDawner and MixedNuts, we have an outline of level 1. At this point I feel it's more productive to post it as-is than discuss it further:
The list has some glaring omissions, like math or chess, because I don't yet know of a crisp enough way to test those skills. Ideas are welcome! Also it seems very likely that some items on the list are wildly miscalibrated, some of them will turn out to be too hard for a beginner, and others will be too easy for anyone with a pulse. I'll be happy to hear about such miscalibrated requirements from the people who achieved them or at least tried :-)
And here's what I think the rules should look like:
Personally, I'm going to try to make the level, but already know that some tasks will be difficult. I hope it's the same way for you.