Milk expiration?

I rely on milk donations to supplement my twins. They go through milk like crazy so I’m always looking for new donors with big stashes. I’ve found a new one through a mutual connection and she has tons of frozen milk but it is 1.5-2 years old. It’s been in a deep freeze that’s only for breastmilk since the day it was pumped. She’s willing to give it all to us (about 5 gallons!) but we know the guidelines say to use it within a year. Our IBCLCs say to “follow the guidelines” but I feel like professionally they have to say that. What are the risks of using milk that’s been in the deep freeze for over a year? Has anyone done it and been ok? We could SO use that big of a donation.