I'd say every hour.
Most important is right after a nap, and right after playing. And there will be a lot of accidents. Getting something like Nature's Miracle or Simple Solution makes all the difference in the world in terms of cleaning.
It is exhausting. We got one at 8 weeks old and he's pretty easy now at 16 weeks. Not perfect. But on a schedule, mostly housetrained, and very social with people and dogs alike. I'd say the first month was really rough (but not human newborn rough!).
We crate trained from the beginning, and also bought a pen (actually two and hooked them together) for safe play in the basement. That helps contain them safely for awhile. I also bought a couple of baby gates so I could contain him in the kitchen so I could get some chores done in there.
Don't need most of that now but still use the crate.
Biting has been a big issue. But he's getting better. We sub toys for our hands, or walk away if he doesn't stop.