Pre post Nuptial agreement

During the Malaysia Merdeka (independence) celebration here in Zurich, I told a friend how sometimes I miss business trips, having not had one for a long time, while when I'd traveled quite regularly in the past, I thought I had a bit too much of it. He shared how he travels quite a lot these days .. and candidly added he also has a deal with the wife 7 days a year he gets to go away on his own alone (so he said). Damn; what a fantastic deal! How come I never thought about such post nuptial agreement? Start to draft it?