You are supposed to tell pensions near every move you make regarding your state pension, they call it a benifit, even if you go in hospital, it may have an effect on payment..
If you live permanently away from the UK in LOS then it means no upgrades, you can to and frow, but you are supposed to tell them the dates, so they may alter payments.
But many folk do chance it to get the extra cash, that's up to you, personally I didn't use family or friends address just in case..????