All CBSA are really interested in is that when you arrive you can appear convincing that you will not need to work illegally before classes start, 5 weeks generally might be on the limit but in reality there is no written guidance and every entry is case by case.
You completed the hard part in getting an offer and a study permit so together with any upfront fees already have an investment that you / CBSA expect that you are not going to risk just by a temporary landing in another city/province without moving on to your final destination for start of classes.