Clearly some eruptions last for a very long time, like Stromboli's 2400+ year continuing pyrotechnic show (see the "How many active volcanoes are there in the world?" question). At the turn of the century the following 15 volcanoes have been erupting more or less continuously through the last three decades (the reporting span of SEAN/GVN) and are likely to remain active for some time: Stromboli and Etna (Italy); Erta Ale (Ethiopia); Manam, Langila, and Bagana (Papua New Guinea); Yasur (Vanuatu); Semeru and Dukono (Indonesia); Sakura-jima (Japan); Santa Maria and Pacaya (Guatemala); Arenal (Costa Rica); Sangay (Ecuador); and Erebus (Antarctica). However, other eruptions end swiftly: 10% of those for which we have accurate durations lasted no longer than a single day, most end in less than 3 months, and few last longer than 3 years. The median duration is about 7 weeks.