CompuServe Messages

If I specify 1000 buffers for my FFS drive, will AmigaDOS automatically give them back when another program requests memory the way FaccII doe? Is there some way to write a mountlist so that one can allocate (say) 1500 buffers amongst _all_ one's FFS partitions, and then have the buffers intelligently decide what to retain and what to let go? I thought buffers were device specific, whereas FaccII uses pooling.