I was curious what if anything was needed to be done and looked this up.
Basic System Maintenance?
Ubuntu checks the file system and hard drive every 30th boot, and doesn't require defragmentation. All ports are closed and hidden by default, so network attacks are rarely an issue. There are very very few viruses/malware/whatever for linux, and the likelihood of them infecting you is slim unless you do it on purpose.
How sweet is that?