Actually, it doesn't stay 'fresh' indefinitely. Home freezers don't get cold enough to completely stop all biological processes, they slow it down significantly and it will last awhile, but certain functions that strip away nutritional benefits continue. There was an article on reefs.com a year or two ago. The article focused on how it pertained to mysis. Mysis gets darker the longer the process continues. If memory serves me right the article recommended only 6-12 months for frozen.