Calibration during Experiment

1
Hello,

I am using an Eyelink 1000 eyetracker and wanted to know if it is
useful to do calibration during an experiment (after some blocks)? Or
for a gaze dependent display after not fixating the fixation cross for
some time! Or is it better to just split the experiment in many parts?

Do you have any ideas on that?

Thanks a lot,

Michael