every time you do an extension you report your address. This is different to the TM30 but you are best asking at your immigration office as they all seem to have different interpretations of the rules.
I asked about this also as I have been doing 90 day reporting over 6 years and she said that's only if the extension exceeds 90 days. Currently they don't for those who were on Amnesty and you have to provide proof of your address every time you apply for the extension