Alberta tar sands have hundreds of years worth of reserves. They're also expensive and incredibly dirty to extract and emit significantly more CO2 during processing than a light oil well will. (The tar is usually melted by heating with natural gas).

I'm quite confident cheap renewable alternatives will make the tar sands inviable far before they run out.

Some good news though, with the war in Iran the spiking oil price means that Albertan executives can ramp up operations and stay quite profitable! Push the price to 200/barrel and we'll just strip mine the entire province after airlifting out Calgary and Edmonton.