The purpose of making a backup is to be able to restore it at some point. Many of the companies I visit do regular backups but haven't ever restored one of them. If you really want to be safe, test the process to pull a SQL Server backup from off-site storage and restore it. I'm watching a company do this right now and they are struggling. We have a trouble ticket open with the backup software vendor to understand why we can't access our backups.
I suggest you test your backups quarterly or twice a year. Want a reminder? I've started a Twitter account for SQLTeam. I'm going to make one post per day. Each post will be a tip or reminder to help you manage SQL Server better. For example, every quarter I'm going to remind you to test one of you backups.