Total solar eclipses are a cosmic accident. They expire in 600 million years.

The Moon is ~400x smaller than the Sun but ~400x closer, so the disks match. It just barely covers it, for now.: You · Near Moon · Far Sun · drifting · ~600M yrs

A total eclipse is a fluke of geometry. The Sun is about 400 times wider than the Moon, so by rights it should swamp the Moon in our sky. But the Sun also sits about 400 times farther away, and those two ratios very nearly cancel. So the two disks look almost the same size from Earth, and the Moon just barely covers the Sun. The Moon is drifting about 3.8 cm farther from Earth every year, though, measured by lasers bounced off mirrors the Apollo astronauts left behind. Once it looks too small to cover the Sun, total eclipses are gone for good.

Perfect eclipses aren't permanent. They're a coincidence we happen to be alive to see.