Yes sure. I used RNA-later to preserve leaves and spikes of barley for a few months. Later, I extracted DNA and RNA from leaves and spikes respectively. I faced no problem.
Yes. We collected different types of fish tissue (muscle, fin clips or the entire fish in the case of a small bodied fish) and preserved in RNA-later. We extracted DNA for whole genome sequencing and we obtained good quantities of high molecular weight DNA. The genome sequencing is being done now.