Visits to Canada are usually approved for up to six months although the final allowed visit time is determined by a Canadian immigration officer at the point of entry.
Leaving Canada and traveling to the United States and then re-entering does not reset the six-month visit period.
Canadian immigration officers are trained to spot any potential visitor that is staying in Canada as a visitor when visiting for another motive such as work, studying, etc.
Marc
2 trips to Canada, only one eTA
Marc obtained his travel document 9 months ago when he traveled with his family to Montreal for his daughter Olivia’s birthday. In two months Marc will travel to Ottawa for 5 days and will have an important business meeting. Since his eTA is valid for 5 years (provided that the passport associated with the eTA is still the same), to travel to Ottawa Marc can use the same authorization used 9 months before to go to Montreal with his family.