I have a boss from India, living in US with an H1B visa and is in the process to get a green-card. He went to Portugal in March 2018, and we processed his Schengen visa via a specific agency provided by the Portuguese Embassy web-page.
At the occasion, we were told that:
"Should he have had a recent Schengen visa from the last 2-3 years, please include its copy and if deemed qualified to submit by mail, we will explain the alternate procedure for him to follow."
The question is: would he need to go in person to a Swiss consulate now, as he has a business trip to this country? And would this be necessary every time he travels to Europe with difference of time higher than 90 days?