1. There is specific time duration for which the LOC remains in force. There is no way that once LOC is issued it would remain effective for a ong time.
2. At the very first place I do not think there was a LOC at all unless your in laws were very influencial and moneyed persons.
3 If the 498A is already closed then carry its certified copy whenever you travel to or from India.
4. To be certain beyond any doubt send RTI to FRRO and BOI and Ministry of external affairs.