Stupid question, but please bear with me because I need to ask it. If the PR sponsor travels for 31 days, is that a short trip by IRCC standards? I know they don't have a definition for short trips, but I'm hoping you've seen enough cases to have a better judgement.
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My understanding is that the only thing IRCC cares about is the time away. They don't care about other factors as much. Is this correct? Will it be better in this situation to cut the time down to 21 days?
If they don't have a definition, they don't have a definition and no-one can say. Neither in terms of how it relates to the facts, or amount of time away, or whatever else.
(Odd it seems if it's your case that eight months since pre-arrival though - have you ordered GCMS notes? Tried MP? Applied for TRV?)
Nor have I seen enough cases to make some overall judgment or guess about what exactly they're looking for. Few enough that I could *speculate* that there's no logic behind it beyond "when a given officer decides to check" at some unpredictable point in the process. Note, I'm NOT saying that it's this random, but that trying to infer what the logic is or was highly prone to magical thinking, as facts could be consistent with a lot of different scenarios - including being entirely random (cant disprove that it's random). (Which some here will argue, "it's okay after [such-and-such eg SA]." I don't think that's clear. The only ones I'd be comfortable saying is after PPR probably fine, and after visa/copr in hand - even more probably fine.)
One quite consistent thing: filing the app while sponsor is abroad - clearly a bad idea. Leaving for lengthy trip right after filing the app and before AOR/SA - looks highly risky.
After that: hard to say and enforcement does not seem consistent.
If you wanted my judgment, I'd say being away less than a month (eg three weeks) is not very risky at all. I emphasize the 'less than a month' esp weeks because, in part, applicants/sponsors seem to want to stretch it out and/or argue what constitutes a 'short trip' (and they do. not. know.). Also because 2-3 weeks corresponds quite well with 'normal' employed-person vacation time in Canada.
30-31 days? Probably only a bit more risky than 3 weeks. But I don't know, and neither does anyone else. Much more than a month? Getting more risky. We don't know that the risk grows a lot or a little (it's probalby not linear).
I think that's about all anyone can say.