Grantbo... about all I can say is thaw some, and test it... sniff it, maybe melt some in a pan and sniff again. I don't think you'll have problems with rancidity (and melting/heating it WILL make that obvious if it is), but I'd be concerned about freezer burn after this many years.
I'd probably make a REALLY small batch and taste test it before wasting a lot of valuable ingredients on the whole amount, too.,
Summerthyme