I had same thought - I suspect there is no upper bound. There are other examples of this sort of thing, but Hawking was new to me.

Hawking! Stephen Hawking!

Hawking hawking. Stephen Hawking peddling aggressively.

Hawking hawking hawking. Stephen Hawking peddling "hunting with hawks."

Hawking Hawking hawking hawking. A throat-cleering Stephen Hawking peddling the idea of hawking

Hawking Hawking hawking hawking hawking. A throat-cleering Stephen Hawking peddling "throat-clearing hawking"

Hawking Hawking hawking hawking Hawking hawking. A throat-cleering Stephen Hawking peddling "throat-clearing Stephen Hawking hawking"