You do not need to upgrade. Non-LTS releases are supported for 18 months, which means you still have a year to go. After that, you may find that updates become rarer and at a certain point, you may find that you cannot access any software repositories for 8.10 anymore because they have been taken offline. If you do not like upgrades, than you should probably hold off until the next LTS (9.10 although it has been suggested that this one may be delayed for six months) because LTS releases are supported far longer than non-LTS releases; however, skipping releases can be tricky affair (although skipping just one is usually not all that bad) and a clean install may be safer if you do.
Upgrading to 9.04 should be fairly straightforward. As always, making a backup of important files is recommended. For potential stumbling blocks with this specific upgrade, check google.