The short answer is, yes, I am familiar with the notice that is required of the crown before it seeks a higher penalty based on a person's prior convictions. That is statutory, so it's not just a practice. There is a requirement in the Criminal Code in section 727 for the crown to give that notice.
That having been said, it's very important to know that the provinces and the attorneys general of the provinces and of the federal government will typically have policy manuals that include guidelines on when the crown should use a look-back period, which means how far I look back before I tender that notice seeking the higher penalty. In some cases it might be 10 years. I'll look back 10 years and if the person is clear for a certain number of years, then I won't file my notice seeking a higher penalty.
The judge is always required to fashion a fit and proper sentence based on all the factors whether they're mitigating, or whether they're aggravating. Interestingly, in Canada, the crown as well as the defence may launch an appeal against the sentence if they believe the judge has not given a fit and proper sentence based on all the circumstances. One can conceive of situations where the notice is not filed because of the policy, but nonetheless the prosecution is asking for more than the minimum penalty based on all the factors surrounding the current offence.