I renewed my passport this year, no big problem. With the new passport you need to make your next 90 day application in person at the Immigration office. There is no reason to register before the 90 days becomes due unless you are planning to travel abroad or do business, but you will need to carry around both passports for around 90 days. Also you need to inform your Bank with lots of paperwork and photocopying and signatures. DHL forwarded the documents to Liverpool HMPO, but I had to collect the new passport in person.