A quote from
http://www.cic.gc.ca/english/information/applications/guides/5445ETOC.asp***
Time spent outside of Canada
You may also count the days spent outside of Canada in the following circumstances as days for which you satisfy the residency obligation:
OPTION 1. Accompanying a Canadian citizen outside Canada
You may count each day that you accompanied a Canadian citizen outside Canada provided that the person you accompanied is your
spouse or common-law partner or
parent, if you are less than 22 years of age
Evidence that you are accompanying a Canadian citizen
You must provide supporting documents to prove that:
The person you are accompanying is a Canadian citizen; and
You are the spouse, common-law partner or child of that person.
Supporting documents may include:
marriage licence
child's birth certificate, baptismal document, and/or adoption or guardianship document
school and/or employment records
association or club memberships
passports or other travel documents
documents indicating the status of the person you are accompanying
***
So, your only worry after your wife lands in Canada and thus obtains her PR status (and a PR card) is to keep some documents you will have to use to prove your co-habitation, which are rather trivial... When the time will come to renew the PR card, you'll need those.