When we've stayed in B&B's we've never been asked not to be in the building during the day.
On occasion we've popped in and out as it suited us.
We tend to go for smaller, family run B&B with more flexibility (or maybe it's a Scottish thing )
every B&B we've stayed at they've never had any rules about when to be out. They've been smaller places (e.g. max 7 rooms), so the owners tend to know when you go out anyway. Some have asked we leave the key with them, so know when we are out anyway. Most do have a checkout time on last day, but are happy to keep luggage usually if you ask or sometimes even extend the time.
(twig -- I'm still trying to remember the great place we stayed in the lakes a couple years ago for your other thread !)