(a) You should have the sample data from each service unit entered immediately after your ride checker(s) has come back from the field.
(b) This has a number of advantages:
(1) reducing the chance of loss of information,
(2) increasing the chance of correcting data errors, if any,
(3) being ready to use the cumulative sample data any time during the sampling year, and
(4) minimizing the rush at the end of the year.