You can't use what you read (or hear) about in situ plantings for your container culture. A good container mix will be very porous and fast draining, often requiring frequent watering. These are all good things! However, it does mean that fertilization needs to be frequent, at a lower dose.

So you have to fertilize container perennials just as much as container annuals?

Their nutritional requirements would change as they enter dormancy or quiescence. Woody plants or subshrubs can be fertilized differently, too. How often also depends upon the type of potting mix, size of the plant compared to the container, and other factors. Herbs shouldn't be fertilized heavily because it might alter the intensity of the flavor.

Again, the quality and consistency of your potting medium is a primary factor in deciding how much and how often to fertilize.