"The dose is the poison" isn't necessarily related to the time; it is related to the actual dose...you're thinking of it in a total, when it isn't; it means at a certain point it is harmful or it is isn't; no amount time could a non-harmful dose be harmful.
Indeed, that is why he calls is "safer models" rather than safe; there are always a risk, but they are drastically minimized. One way they are minimized is taking enough test to work, while avoiding AIs, which are detrimental to our health, is just one example.
The behavior in question is the actual blast/cruise model, which is harmful in of itself, while people think it's not, while also completely avoiding the most toxic and harmful drugs, using only those studied in humans.