Optimal RNA preservation pre-sample prep over long time

[Noa]

I have an experiment planned in which RNA samples will be collected during a clinical study over the course of a year. I plan to use Qiagen RNeasy Micro kit for RNA prep

Which is the best option to minimize biases and maximize RNA stability and integrity (for future use in RNASeq):

1) Save cells as pellet in -80C; prepare using RNAprep kit after all samples are collected (roughly 1 year storage time)

2) Start RNAPrep procedure, adding the first buffer and homogenizingg; saving homogenized cell lysate for up to 3 months in -80C; and processing collected samples every ~3 months.

3) Prepare each RNA sample immediately and store as RNA in -80C until ready to perform library prep on all clinical samples simultaneously.

Happy for advice on best method and rationale!
Thanks
Noa

[luc]

I do not have any data to support my opinion.
I would go with number 1, due to the consistency of the RNA isolations - they will be all prepped at the same time by the same person. RNA is stable if stored right.

You could also extend option 2 to store the sample in RLT for the entire year at -80C.