I wouldn't spend more than two, three days in Banff itself. Instead, use the town as your launchpad for getting into the spectacular folds of Banff National Park, plus to experience Lake Louise, the Icefields Parkway, Lake Moraine, and Jasper. Banff is nice enough, though it does get a little overrun in summer. All told, I'd give yourself two to three weeks to get the most out of the entire area. If you're there in winter, of course, Banff is a little less of a zoo -- but with more Aussie ski bums. That's because you've got a huge variety of skiing in the shape of Banff-Norquay, Sunshine Village, and Lake Louise (not to mention, Marmot Basin up in Jasper). More skiing-specific info for Alberta at: http://away.com/skiing/ski_location.tcl?Alberta_Skiing&id=293107.