Question

How does the ring system of jovian planets persist for so long?

Answer 1

Rings should not last for very long: collisions between ring particles will cause them to spread out over time, destroying the thin ring.

Thin rings, however, can be gravitationally confined by a pair of Shepherd Moons:

Outer moon's gravity decelerates ring particles, moving them into lower orbits (eccentric ellipses smaller than the original near-circular orbit).

Inner moon's gravity accelerates ring particles, moving them into higher orbits (eccentric ellipses larger than the original near-circular orbit)

Subsequent collisions between ring particles then damp out the eccentricities, resulting in the ring becoming confined between the Shepherd Moons.