It can be a few hours at least to Lake Louise, depending on how frequently you pull out to stop. I'd spend a night or to at LL in your shoes, probably. The shuttle bus system does stop at the campground at Lake Louise, as I recall, so you don't need to go find parking if you stay at the campground and take the bus...which is what you really, really, really want to do in the peak season. The same can be said for Banff and probably Jasper, too. (There are overflow parking areas that are served by the busses, too, which work out okay.)