Medicals are only good for a year. Last year they changed the process so they could be extended for an additional 12 months, but that wouldn't apply to you at this point.
No, the 8 months is the time for 80% of applications to reach the "Decision Made" point - you are already there. The only thing required in your case is the local office confirming your medicals are current (even though there's no chance that those results will change the decision - it's a statutory requirement they be current) then they should schedule your landing appointment.
You should contact the call centre. It is possible that they do not know your medicals are done, or your local office has not yet looked at them, but in either case, five months after you received DM is a very long time to wait for a landing appointment even if you had to do a re-medical. If they won't tell you anything useful, you should order your GCMS notes (search the CIC website for "privacy act" and you will find the forms - there is no charge to order your own records as long as you are inside Canada, which you obviously are.) Your sponsor should also contact the MP for your district in that case, because political pressure usually brings good results to cases like yours.
You should be a permanent resident LONG before October 2013. Indeed, you should have been a permanent resident by now.
Good luck!