U wrote:
"Lets take a scenario as an example. Suppose, you have done your medicals on 1st January 2013 (which would expire after one year automatically on 31st of December 2013) and today if you gets your visa where the expiry date is mentioned as 30th June 2014. Now, keeping in view this scenario, you must land in Canada before 31st of December and there is no benefit of having a valid visa till 30th June 2014."
No offense brother, but This example is incorrect. Coz visa office would NEVER issue u visa validity till June 2014, IF your medical expires on Dec 2013
they r not idiots...they calculate the validity (of both, medical+passport expiry) carefully while giving u visa.