The article is talking about kilogram-scale amounts of helium-3, so lithium abundance (billions of tons) isn't remotely a factor.

> "there would be a helium-3 shortage decades later"

There's a conceptual misunderstanding: radioactive decay is continuous—there's no latency of waiting. You get a stream of decay product right from the start.

> "economically infeasible"

It's the sole source of helium-3 today.