My last application took more than 3 months, but they will count your renewal from the date they receive your application.
Once your submit your application, relax, even if you haven't received the new one. It will take some time. December is a slow month because of the holidays.
Renewal of a visitor's visa consists of a visitor's visa and a temporary resident permit. The latter is automatic. However, if you renew your visitor's visa after the expiry date, you will have to reinstate your TRP for a fee.
Submit your application now - 60 days is a reasonable time.