Well, I think it's generally wise to take breaks from any herbs, supplements or protocols like Bob Beck's.
But from the (admittedly messy and contradictory) online information I've read about ionic- Colloidal Silver , I think your client's experience sounds highly unusual.
I'm not doubting it happened, but 2 tablespoons a day of 5ppm ionic- Colloidal Silver (i.e. made as Sota now recommend with distilled water, no salt, controlled current etc.) causing a dangerous build up of silver in the blood after five months doesn't seem to reflect most people's experience.
But I accept it as a useful caution about the importance of taking breaks from it - trust me, I've no plans to go wild :-)
Incidentally I thought this was an entertaining refutation of the quackwatch fist-thumping brigade's dismissal of Colloidal Silver :