If you're happy with the image you're on, no need to keep updating.
However, updates contain bug fixes, new features & so on...
Also, the longer you leave it between updates, the bigger chance an older settings restore isn't recommended.
Saying that, we have users who update daily, weekly, monthly, yearly & even longer.
Updated builds are announced on the forums, facebook & twitter, so shouldn't be too hard to decide on what you want to do.