It depends on how many staves I have to do. I have 2 reflex cauls and have done several a day. By the time I get another growth ring chased and reduce the stave to steaming dimensions, it's been about two hours, and they behave pretty well unclamped at that time. If it was a severe correction or I don't need the caul, I leave it in there at least a day, sometimes a week... and they do seem to stay put a wee bit better that way.