Hi SSkundu ( and Sulnata) -
Inside Switzerland, allowable connections (as far as the scheduling computers are concerned) are typically 4 minutes, perhaps a bit longer at big stations such as Zürich, with multiple track levels. Luzern is a single level station with (I recall) 14 tracks, all of which terminate at one railhead platform. 4 minutes is fine, even with luggage.
At Arth-Goldau, which is a transfer point for trains from Milano Centrale to Luzern and Zürich, and where possible for common connections at many stations (such as Spiez) , connecting trains will be stopped at the two opposing sides of one platform. At Arth-Goldau, a lot of people make that change, which can be done in one minute if you don't have a lot of luggage, you just walk across the platform. The trains from Italy to Luzern then onward Basel, or alternately, Zürich and onward, all stop at Arth-Goldau, so that you can take a train to either Luzern or Zürich and (on average) half the time, you'll have to get off and change at Arth-Goldau.
The nice thing about Switzerland's system is that there is almost always another train along in one hour. Since reservations are not needed on any and all trains and buses and boats, except for a few rare excursion trains such as the Glacier Express, that works well. The SBB is well along in establishing service every 30 minutes between stations such as Bern/Zürich, because they want to make the main lines into fast and frequent interurban service. Their plan is to allow you to walk over (or take a tram every 8 minutes in the cities) to the station and catch the next train without worrying about schedule.
In the Bernese Oberland, trains from Lauterbrunnen to Kleine Scheidegg are scheduled ever 30 minutes. In high season, when the small trains are quite full, unscheduled trains are often fitted in between the regular ones to carry the large number of passengers.
On systems that require reservations, which are essentially all other countries for main line or international service, SSKundu has presented the dilemma. If you miss, you need new tickets. Not so inside Switzerland.
The once per hour rule for services is sometimes broken on secondary lines or, especially, bus lines, at midday or early afternoon, out in the countryside. And, some services do not run late in the evening. For the routes that most tourists take, that does not happen. I sometimes run into it if am taking a bus to a trailhead for a hike.
The timetable is useful for that reason:
The Swiss timetable will show trains from Milano Centrale to Luzern. Sulnata can easily check to see when the next train is and perhaps take a later one. The service is fairly frequent.