There is no way to guarantee what time period a visitor will be granted other than to recommend being honest and convincing answering any questions on purpose of visit, return ticket (no need to show unless asked to show), funds, itinerary and one that sometimes catches people out when did you last visit. Other advice is to not volunteer information just be polite to the CBSA officer and only answer questions asked else you can just go down a path you might not want to unecessarily .Follow this and should not be any issues in getting a full stay.
