Do I need to keep my node updated, and how often?

Yes, you should apply node software updates in good time, especially releases that touch consensus rules, because running an outdated version risks falling out of step with the rest of the network. You do not need to chase every minor release the day it lands, but you should not let your node drift far behind either. Read the release notes before upgrading so you understand what changed, then stop the node cleanly, update, and restart. Running your node as an auto-starting background service makes the restart painless. A light maintenance log of when you updated keeps future troubleshooting simple.