I have found if I cheat hardly at all, I go out of ketosis. But if I behave myself, it just takes me about a half a day to get back to moderate ketosis according to the strips. I usually only use them once a day in the morning, but I've experimented with them lately to see what it takes to pull me out of it. I too was suprised at how fast I got back into it....

Hope your DH is doing fine!