Hi
I heard somewhere that if you go for 5 months you need to at least wait the remaining month to expire before you reenter because if you reenter before it will be as if you continued your 5 month stay...
Like I said... I heard it somewhere (not to be taken seriously)
there is no set time that you have to leave, if the IO thinks that you are residing in Canada permanently, but just leaving every 6 months, s/he will refuse admission. Especially if you have no ties, job, school, home in home country.
PMM