I think the reason for extending the ability not to get a record or a suspension of a record for a longer period of time does act as a deterrent for that individual from actually committing another offence, if they're sincere about moving past that time and getting on with it.
It has been felt that three years is simply not enough time to make that assessment. The five years, in the case of indictable offences, is simply not enough time to make that assessment, recognizing, though, that there should come a time when these individuals should be in a position to apply for that suspension of record.