Even 20 years is much below what most studies show. Panels tend to keep functioning well beyond 30 years, with degradation at 86%. It might be true that economically in 30 years they're so much cheaper that it's worth replacing them with new panels, but that's an optimisation, not a question of replacement need.

Inverters a different story.

Nobody is retiring solar panels after only 20 years.

5 years is the worst case estimate, with 20 years lifetime this dependency on China is even less bad.