Yes a flew back twice. There was less than month between the flights and not much lead time either. Cpouple of weeks lead time if I remember correct.
I didn't explain being abroad and it's not forbidden to leave Canada during application process as long as you have valid PR to the end of the process:
https://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=911&top=5
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"
Can I leave Canada after I mail my citizenship application?
Yes. You can leave Canada after we receive your application.
If you need to leave Canada and want to stay eligible for Canadian citizenship, you must:
- make sure that you live in Canada long enough to keep your Permanent Resident (PR) status
- be a permanent resident (when you apply)
- not lose PR status before you take the Oath of Citizenship
- bring your PR card with you when you leave Canada so you can return easily"
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So, leaving Canada is not an issue, but it's still good to make sure to be able to participate both test and oath as well as have access to Canadian mail in case IRCC sends regular mail instead of email.