Except this is what you have said:
What I am thinking is, I would like to submit my application in Canada, with around 760 days count, and go back to original country for 1.5 month ( I do have nothing to do in Canada), and return Canada before the PR card expiry date.
So with barely meeting the requirements you would travel to your home country (instead of to USA to stay with your wife). So if ever some days in counting are close to those 5 years (like 5 years ago). They would be consumed without renewed. That is why it can backfire on you.
And because of your back and forth travelling, they can question all of that and force you to show detailed itinerary of all your travelling. between 3 countries.
That is why I meant that it can backfire on you.
Thanks for your point. For "detailed itinerary", is the stamp on passport enough? Canada never stamp on its citizen or PR's passport after they are entering since equipping scan machine in airport and never stamp any passports when people are leaving. But CBSA has all those records. Do I have to ask CBSA to report my records first?