Glak1234,
I think you misunderstand what others have been telling you...it is not necessarily a good thing to prove that you "live exclusively outside of Canada", neither is it a bad thing, but if you are able to say that you are just visiting it will be much better for you, because it's one less thing you have to prove. For a sponsor who lives outside Canada, the hard part is not proving that you are outside Canada, but rather that you will be returning with your spouse when they receive permanent residence. However, you said that you plan to move there to live with him until he gets his PR card. Does this mean that you will not have a residence, or a job, or bank accounts, or any ties to Canada? Does this mean you will be applying for residency there or just be there as a visitor??
If it helps, I also am a sponsor living outside Canada. I sent in a declaration saying that I would be returning to Canada with my husband. I sent in bank statements, Notice of Assessment showing I am up to date with my taxes. A letter from my sister saying we will be staying with them at the beginning, until we find a place to live. I also have a job offer from the company where I worked before I left. What the government is really interested in seeing is that you will not be needing their assistance when you return to Canada. That you will have a way to support yourself and your spouse, and a place to live. That is what you need to concentrate on, if you're going to to say that you are living abroad during the application.
There is no specific timeframe (that I know of) that you have to be outside Canada, before you are considered to be living outside Canada. I sent in my resident card to show them that I was living outside Canada.