Yeah the Nigerian government made this decision to combat the high rate of counterfeit money in circulation and also to combat hoarding, it turns out most of the corrupt politicians are hoarding tons of naira notes for their selfish interests instead injecting it in the economy for growth.
This sudden decision by the government to change the notes forced majority to bring out these notes they have safely hoard in strategic locations. It is sudden but a good decision. Like you said, it something that should be done in every new administration.
The idea may look good but there are some disturbing pattern in the process.
1. There was no consensus on the process among financial personnel, it was all between the Governor and the president, which is considered inappropriate.
2. Some view the decision as a witch hunt against those who denied him the opportunity to run for president on the same basis that the same governor expressed interest in the presidency, who should be investigated.
3. A similar redesign was done 40 years ago when the president approved it, which cannot be attributed to any changes in the currency's value.
4. In view of the fact that the redesign of the naira is very expensive and the country makes complaints about the state of its economy, why the decision now?