Just to illustrate how subjective this question is - about 10 years ago, I bought a 1939 Farmall tractor from the son of the original purchaser. The family had actively used the tractor on a small farm from new until a few years before I bought it, it had unknown thousands of hours on it.
It clearly had a (minor) headgasket leak. The son (who was in his late 60's at the time) told me he'd been topping up the coolant every few weeks since he was a child. The headgasket had been leaking for at least 50 or 60 years when I bought it, yet the tractor ran okay.
Clearly, that motor is significantly different than the one in your vehicle, and I would not advocate for letting a headgasket issue go unfixed for half a century - but, the point remains: it's pretty difficult to guess if or when a headgasket leak will lead to serious issues.