What happens after 180 days? I don't want a vault for which I'll lose the key in 180 days.

Many people actually only need it for a few days, like when travelling away from home or office. Most people care about data (and computer or laptop) loss when travelling away from home rather than at home. That is the rationale behind the 180-day version, which is full featured with nothing grayed out or blocked. After 180 days, one can decide whether to take the data out to stop using it or to get the perpetual license.