They'll last a long time vacuum packed in the freezer.
I buy a lot when they're on sale (usually a year's worth):
However one year when they were $4.99 a pound I bought 10 Prime Ribs for $350 during Christmas Week.
I still had a few left when I went in the hospital a year later.
Then after a month in the hospital, I came home, and my taste buds weren't working properly, and everything tasted terrible, so I didn't smoke any Prime Ribs.
I started getting my tasting ability back after about 7 months, and was finally able to enjoy Smoked Prime Rib again.
The last Prime Rib from that batch had been in my freezer for at least 2 1/2 years, and it was just like new!!!
Bear