The first source I quoted said a "a few hours or days," but I guess that wasn't convenient for you, so you clipped it.

The numbers 5 and 10 are means. "A few hours or days" represents a range. If you look at the first study, there were several participants who never had detectable spike protein, even when they first checked on day 1 after vaccination. So the spike protein cleared in less than a day for a large chunk of people (i.e. "hours").

As for which study I would trust more, the first study (that reported the shorter period had four times the number of patients). But I guess that is also not convenient for your narrative.