Now to a trick: If you do want to distribute an AffyBatch object, have
a look at your intensities. If your chip type is a 3x3 pixel per
probe array, and the Affymetrix image analysis (typically) took the
75% quantile (7:th ordered pixel), you will actually see only integer
probe signals. Note, this is not a rounding error but it just happens
"by chance". If this is the case with your data, you could create an
object holding the signals as integers and not doubles without loosing
anything. That object would be roughly half the size. I don't think
compression algorithms can pick this up.