I would add that it's not only the time, but also where.
My concern would be that if you want to eliminate the scenarios that I think are quite possible and probable, given the entrepreneurial nature of the private security industry and how they want to differentiate themselves from other competitors as to who is more aggressive, more cutting edge, and so forth, you might be put in the uncomfortable position of at least thinking about the fact that the subsequent arrest has to take place on or in relation to the property on which the person was actually first caught doing it.
Second, in my experience, if it starts to go beyond a day, I think you'd agree that you're talking about the private security people delaying for the purpose of conducting investigations.
So I would say one day, and again it has to be somewhere around the property.
I don't think that satisfies your colleague, but it makes me as a citizen feel a little more secure in knowing that there are constraints around this.