Variation of conditions of probation and discharge of bonds executed by offender

The court before which any offender is bound by his bond under section 4 to appear for sentence when called upon,– (a) may at any time if it appears, upon the application of the probation officer, that it is expedient that the bond or bonds executed by the offender should be varied, summon him, and if he fails to show cause why such variation should not be made, vary the bond or bonds by extending or (a) diminishing the duration thereof (so, however, that it shall not exceed three years from the date of the original order and shall not extend beyond the date on which, in the opinion of the court, the offender shall attain the age of twenty-five years), or by altering the conditions thereof or by inserting additional conditions therein, or (b) may, on application made by the probation officer and on being satisfied that the conduct of the offender has been such as to make it unnecessary that he should be kept any longer under supervision, discharge the bond or bonds executed by him.