Linda - we run one control for each batch of slides stained in a run and I
think that's what most people do. If your docs insist on a control for each
patient, try mounting the control close to the top of the slide and then
mounting the patient, when cut, on the lower portion. That way you've got a
control for each slide and you're saving slides and space, though your control
use will stay the same (and with Giemsa stain those controls aren't  always
easy to find!)