Tom
Yes, those were the days when it was cheaper for my company to pay for a round ticket for my wife and an extra night or two in the hotel (needed a Saturday night), than for me to leave and return during the week (going to Paris or Brussels).
Ok, strange. I did the exact same overlapping thing for many times. I had a job that required flying to Stockholm twice or three times a month, often on short notice. If you book a flight leaving tomorrow and coming back in two days do you get crazy prices... so I always made them overlap to have a Sat to Sun night in between - which was at least back then the secret tip to cut the price in half. Never had any issue or even comment... but that was a route where Swiss and SAS were competing, so I would not be surprised if airlines would exactly analyse the routes you fly to determine if they should call you or not...
I thought that was just part of the Swiss immigration control policy.
Zurich Brussels return 1,100CHF - yes those were the days
Indeed, free champagne, great food.
But only CHF 350 if you stayed Saturday night, hence cheaper to take the wife and stay another night!
Tom