I understand your concern Rory, but BSP have stated there will be no demonetisation ( removal of currency ) " during the Governor's term ", and they have given advance notice of currency changes in the past.

https://www.manilatimes.net/2021/12/...-watch/1825963

Even when the "New Generation " banknotes replaced the " New Design " banknotes, the public could still have the old banknotes exchanged at authorized financial institutions like universal and commercial banks, thrift banks, rural banks, and cooperative banks.