Without maintaining your WordPress installation, you make yourself vulnerable to hackers. They will find security holes through WordPress itself, your theme, or your plugins. This is why it is important to keep up to date with your software. Unfortunately, updating a plugin can also break your site. Before updating, I always make a backup, so I can revert if necessary. While this can take anywhere form five minutes to five hours, you pay the same, and I don’t stop working on it until your site is functioning correctly.