Well, except for the next release. Oh, and also any issues we have with this release. And feedback. Now that we're in production we're going to get even more feedback.
Feedback comes in many forms: comments and emails from users, bugs from support. There's another source of feedback, though: the system itself. The system speaks to us in ways customers can't see: log files, data logged in a database, files created on a file system, and the like.
Take the feedback your system provides. Get the logs from production (go bug Ops if you have to) and take a look. Any warnings? Errors? Things happening more or less often than you expect? Check out a dump of the database, too - what's null that shouldn't be, or has weird combinations of values? That's probably something you should look at.... even if it hasn't manifested as a problem yet.
A good system is clean from top to bottom, from UI to logs. Take a look at your system - is it clean?