you have to store it @ -80 degree celcius

I store at -80C, never stored at -20C.

LN2 is best if you have that option.

Yes, you can store RNA at -20 degree Celsius as ethanol precipitate or solubilized in formaldehyde for up to one year. However you should note that RNA is generally stable at -80 degree Celsius in an RNase-free medium.

-80

RNA long-term storage solution is the best solution for the inhibition of reverse transriptase activity , better to store your RNA in -80°c