After spending way to much time on google
I found this paper on banana seed germination and storage.
"Germination and storage of banana seeds" by Chin, HF.,1996
Banana seed dried properly can be stored at below freezing temps.
If the moisture content on the seed is below 10% they can even be stored in liquid nitrogen for 12 months, with 44% of the seed still germinating. All seeds stored with a moisture content of 16% and 29% failed to germinate after 3 month storage at the -196C temps. At 6 months he still had 65% and 58% germination with seeds containing 10% and 16% moisture, while seeds with 29% moisture were 0% at 6 months.
He also said with the proper drying banana seeds can remain viable for 2 years. And I read somewhere that ensete seed have remain viable for 25years in the ground before the dirt was disturbed and germination took place!
It was also noted that seed viability can be tested using a 0.5% solution of tetrazolium chloride. The seed embryo will stain red in viable seed.