You could spend up to 6 months a year in Canada on a tourist visa. (say during the summer.) I don't think as a retired individual you would want to spend your winters in Canada anyways. (Ottawa had the honor of being named the world's coldest capital city 2 days ago.)
As long as you maintain strong ties to Australia/a non-Canadian country and spend more time outside Canada than you do inside Canada (say a 5 month/7 month split) and have enough money to take care of yourself I think Canadian immigration will have no problem letting you into the country.
I know you asked about Canada, but on the topic of retirement destinations:
Many European countries have various options that provide more permanency. Though not a retirement program per se Spain and Portugal have a residency through residential investment program. (400,000 EUR min purchase though) Greece offers residency through residential investment if you purchase property for 250,000 EUR or more.
Another attractive (and far cheaper) option is France. If you can prove sufficient financial means (I think it's 15,000 EUR a year or something of that sort) and show proof of medical insurance valid in France they will issue you a long-stay visitor visa. Once in France you get a resident permit from your local commune valid for a year which can be renewed yearly as long as you sufficient means. The actual cost of getting the visa and permit is barely a few hundred euros.
An EU residence permit also comes with free movement in the Schengen zone, so you don't necessarily need to live in the country that issued your permit. (Though technically the maximum allowed stay in other countries is 90 days every 6 months, it's not enforced due to lack the immigration checks inside the Schengen zone and only becomes an issue if you try to claim social assistance or something of the sort.) Thus you could take a residence permit from France but live in Holland.
Best of luck!
