The quick answer is it depends on the circumstance. To go into more detail, the majority of places on my list were port calls during patrol periods when I was stationed on a cutter. These are typically 2-3 day visits where you may or may not have to spend a day on the ship due to normal duty standing, fueling, logistics, maintenance, etc. Port calls are great because they give the crew a break from the patrol slog, allow for more innovative connections to back home (FaceTime, Skype, WiFi, Texting, etc.), and give you some cool adventure opportunities (Waterfall Rappelling in Costa Rica for example). Other trips have been for temporary duty via plane, my visit to Italy was about a week, both my Italy and Canada trips were done while at the CG Academy as well the Ireland/England/Germany tour on the Barque Eagle.
That being said, the CG does have plenty of international opportunities, including permanent stations from the Pacific Islands to Far East Asia, to Europe, etc. These tours are typically at a higher rank, usually Lieutenant Commander (O-4) and above with a few Lieutenant (O-3) billets sprinkled in. There are Coast Guard Cutters and land units permanently stationed in the U.S. territories of Guam and Puerto Rico where yes, you are there for anywhere from 2-4 years. That being said, "back at port" every night is rare for any ship...particularly ones that officers are stationed aboard. The smaller cutters (think 87, 110, and 154 foot vessels) can operate from a few days out to 1-2 weeks before they pull in to a port (and not always their homeport) while larger cutters can be away from land from one to a couple of months depending on logistics and fuel. On a 270 foot cutter, the longest I was away from land was 32ish days.
All that aside, I've had some incredible opportunities in the CG in just four years. Your DS will undoubtedly have the same as long as he continues to put the work in. Congrats to him on earning his appointment!