Why does food spoil in the freezer?
Most freezers are frost-free, which means that they occasionally cycle above freezing to prevent formation of frost on the walls of the freezer. This makes them easier to maintain but it shortens the storage longevity of the food. 

This makes products stored in them vulnerable to freezer burn, which is a loss of moisture. It can also cause ice and IQF products like frozen fruits or vegetables to solidify into a single mass. If you have ice cube trays, you may even notice them becoming empty after a few months of sitting unused. 

Freezer burn is a loss of quality, though, not a health issue. The food isn't spoiling. 

If you have a "deep freeze" or a non frost-free freezer that you only access occasionally, you can certainly keep foods for nearly indefinite periods of time without worrying as much about freezer burn. 

You can also reduce the likelihood of freezer burn by following better freezer practices. 

Resources available here and here and here.