The residencia (actually just showing you are on the register of EU foreign nationals residing in Spain) is valid (at the moment) for life and never needs renewing.
You do, however, have to ensure the address is changed to match your new one. There are some town halls (not all) that allow you to do this whereas with others you will need to attend a national police station or foreigners' office to do this. You need to complete the EX18 again and tick the bottom box under Modificacion and cambio de domicilio.
Make sure you have your old residency card with you which will also show the NIE number.
If the new rules come in (and you are a UK citizen) that may require us to get an ID card for permanent residency then having an up to date old one may ease the process.
There is also an online site Informing of Changes but I found it quite difficult and never received my electronic signature to do so. It also takes two months after you have updated your padron for it to go through the system which may be a little late.
This message was last edited by mariedav on 30/08/2019.