Permanent residents don't always become citizens. The bar for citizenship is higher.

If you're living in Canada, you must have been a permanent resident and physically present in Canada for at least 1,460 days (four 365-day periods) in the six years immediately before the date of your application.

You must also be present for 183 days (half a year) during each of the four calendar years that are fully or partially within the six years before the application date.

In other words, your time in Canada needs to stay relatively consistent.