Two years. I think. Unless he said three. But I think it was two.

It sounded like he'd used ALL the muggleborns but that can't be right because he didn't get Maureen, did he? he'd run out suitable mudbloods, was what he said. I think he said there were fifty-three of them but it took a lot of experiments and I think a lot of them just died and he didn't get any of the potion. Elixir. Whatever.

Mr Strangeweale did drink some of it himself. He gave some to others too but I guess some of them it didn't work properly and it made them older and sicker instead of younger and stronger.

And yeah its too bad that didn't happen with the elixir Mr Strangeweale drank.