Many governments-in-exile are relatively limited in time. For example, during World War II, occupied countries like The Netherlands had governments-in-exile. However, some exist for a long time. For example, the Rada of the Belarusian Democratic Republic has been a government-in-exile since 1919, almost 100 years, waiting for Belarussia to become a democracy.
How do democratic (or "democratic") governments-in-exile, such as the Rada of the Belarusian Democratic Republic, choose their members of government? For monarchies, the answer is quite clear: someone claims the throne and this is inherited as if they were actually in power. But in democracies, a government is normally formed after elections. Such elections are impractical for a government that has no control over any territory. Then how do they decide who is in the government-in-exile? Are there elections among some registry of the diaspora?