Confucian systems were practiced primarily in China, Korea, and Japan. In China it resulted in four dynasties that approached the three century mark. If you count the Han who instituted it as a single dynasty (admittedly arguable), you have a four-century dynasty right there. In Japan it seems they've only ever had the one imperial dynasty (though Shoguns, blah, blah). But witness Korea, the most consistently Confucian of the three. Korea's preunification dynasties both lasted roughly 700 years, the dynasty that did the unification almost made it to the 1000-year mark, the last two made it 474 and 618 years, and the shortest dynasty was 228 years long! Of course Korea is also closer to the size of European kingdoms, which occasionally did have long dynastic reigns.
Joseon lasted 618 years, while Goryeo lasted 474, as you stated. However, Silla lasted around 600 years post-consolidation, of which only 267 were "post-unification." The record-holder is probably Goguryeo, which arguably lasted well over 700 years if the foundation date is assumed to be closer to 50 BC, instead of the 37 BC date as stated by the
Samguk Sagi, as the regional nomenclature first appears in Chinese records in 113 BC. The dates are uncertain before 668, as Goguryeo was consolidated in 37 BC, AD 3, 313-4, 396, and 427, while it was not until the mid-4th century or so that Baekje, Gaya, and Silla fully absorbed the remaining Mahan, Byeonhan, and Jinhan statelets, respectively.
In addition, while Gojoseon was arguably founded in 2333 BC, it probably underwent two main periods of consolidation around 1500 and 700 BC, according to archeological evidence, although it probably remained as a close confederation of various statelets. On the other hand, there is no consensus on how long Buyeo lasted, and the widest range extends from the 5th century BC to AD 494, although it appears in Chinese records in the 3rd century BC, and was greatly weakened soon after Goguryeo first began to expand during the 1st century BC. Goguryeo and Baekje also both incorporated Buyeo's founder (King Dongmyeong) into their state ideologies as well, further blurring the distinctions.
The other three dynasties were the Jin, which lasted around the 3rd-2nd centuries BC before becoming the Samhan (Three Han), Balhae, which existed concurrently with "Unified Silla" during the North-South States Period for 228 years, and Later Baekje, which only lasted 44 years. As a result, Later Baekje was arguably the shortest lasting dynasty.
To sum up, the longest dynasty was Goguryeo, while the longest unified one was Joseon, and Goryeo only lasted 456 years if pre-unification is ignored. Most of the reason for this was that Buyeo, Goguryeo, Baekje, Gaya, and Silla were able to withdraw to their core regions during times of extreme crisis, along with taking advantage of strife between or among other rivals, significantly extending their durations. On the other hand, Goryeo fell earlier than Joseon did because it endured invasions from the Liao, Jurchen, and the Mongols, and eventually collapsed after a coup was staged before a suicidal invasion of the Ming had been carried out. In comparison, Joseon only suffered two major invasions (Japan under Hideyoshi, along with the Manchu), which were collectively less destructive than those of Goryeo, allowing it to remain highly stable for the longest period of time.