As others have suggested, a big consideration is being sure to have enough of a margin over the minimum to
(1) be sure there are no mistakes that could reduce the number of days to less than 1095; just one day short would require DENYING the application;
(2) have enough of a margin over the minimum to avoid concerns about meeting the presence requirement in order to reduce the risk of non-routine processing and potentially lengthy delays
The second of these is a personal judgment call. The first is critical, as it makes the difference in whether the application is denied or not. The second is about reducing the risk of lengthy delays. Applicants who go abroad for extended periods of time while the citizenship application is in process PROBABLY face a significantly increased risk of non-routine processing and delays anyway.
Beyond that there are logistical risks, which others have addressed, the main ones being the risk of missing notices or otherwise failing to timely respond to requests or failing to appear for a scheduled event.
Comments asserting that IRCC does not stop processing a citizenship application "
just" because the applicant is outside Canada tend to be misleading, glossing over the potential for a total stranger bureaucrat having questions leading to concerns, leading to elevated scrutiny and non-routine processing. It warrants noting, in particular, that historically CIC/IRCC has in fact long approached extended absences after applying as a potential
reason-to-question-residency and there is nothing in currently published information which says current policy is otherwise (many quote IRCC policy statements about TRAVELING abroad while the application is pending; living abroad is NOT the same as "traveling" abroad).
It appears this is NOT a focus of concern to the same extent it was in the past (indeed, for a short time, under the Harper government, living abroad while the application was pending was a stand-alone ground for rejecting the application, based on a statutory provision the Liberal government repealed). Moreover, even when it was a focus of attention and concern, anecdotal reporting in forums (including this one) suggested that citizenship applicants who were abroad for more or less obviously temporary reasons, including to attend educational programs in particular, often did not encounter the elevated scrutiny, non-routine processing, or delays that others did when they simply moved abroad or went abroad to work.
All of which is to (1) recognize that applicants abroad for extended periods of time tend to have a higher risk for non-routine processing and delays, but (2) the extent of the risk is very difficult to discern and appears to vary considerably.
Overall, to be clear,
going and staying abroad is NOT PROHIBITED. BUT there are RISKS. Logistical risks. And a difficult to assess risk of elevated scrutiny, potentially non-routine processing.
The latter, the risk of elevated scrutiny, should be a key consideration in how much of a buffer over the minimum presence requirement the applicant has when making the application.
