The declaration means absolutely nothing... what is important is to meet the requirements. You can declare yourself a non resident, it won't change a thing if for example you come here for two years on a leave of absence and have a job waiting for you back home.
At the end of the day, it comes down to the audit. CRA will check if you meet the requirements or not. Many of the tax lawyers I know have mentioned that sending paperwork beforehand may raise flags and make you a more likely target for audit therefore they advise against it.
Some people opt to get the CRA to rule on their case beforehand(essentially and audit) if there are ambiguous matters or special circumstances such as a spouse living in Canada.
The bottom line is that to be safe, you have to sever ties and not demonstrate your intention to return in the near future. Renewing credit cards, driver's license, health cards, having a spouse there, a job waiting or a residence that isn't rented at arms length all demonstrate an intention to return. That's what needs to be avoided...
As always, the best advice may be not to listen to know it all posters on a website but to consult a professional tax lawyer if in doubt.